Pictured: Three suspects charged

Three foreign surfers in Mexico were allegedly killed by a trio of robbers because one of the men refused to hand over their vehicle during a carjacking, authorities say.

The men may also have been targeted because their truck had American number plates, although this theory has yet to be confirmed by police.

Australian brothers Callum and Jake Robinson and American Jack Carter Rhoad were last seen on April 27 in the Mexican province of Baja California.

Jesús Gerardo Garcia Cota, alias El Kekas, and his partner Ari Gisel García Cota have been charged after police found four bodies at the bottom of a well on a ranch in northern Mexico. Cristian Alejandro García, the brother of Kekas, was also charged.

All three of the suspects were in possession of an assortment of methamphetamines and other illegal drugs at the time of their arrest, according to Zeta and Talk Baja. 

The trio was arrested during two police operations on Wednesday, May 1 - with 23-year-old Ms García Cota reportedly found in possession of one of the missing men's mobile phones.

The bodies discovered in the well have not been formally identified by police; however, Border Report and FOX 5 San Diego are reporting they are the bodies of the missing tourists, citing a source in the Baja California Attorney General's office.

TV network Milenio is also reporting physical characteristics, including hair and clothes, means there is a 'high likelihood' the bodies are those of the three surfers.

The fourth body is reportedly the ranch owner who had been missing for several weeks, according to Zeta. No cause of death has been made public.

'It is presumed [the bodies] are the ones being investigated,' a state prosecutors' office employee told Milenio.

'A fourth body was located. It is not related to the three foreigners. The fourth body had been there for a long time.'

Brothers Jesús Gerardo Garcia Cota and Cristian Alejandro García were two of the three arrested. It is unclear which brother is which in their mugshots

Ari Gisel García Cota, 23, is one of three suspects arrested. She is reportedly the partner of Jesús Gerardo Garcia Cota, who was also arrested

The trio was arrested during two police operations on Wednesday, May 1 - with Ms García Cota reportedly found in possession of one of the missing men's phones as well as illegal drugs

Australian brothers Jake, 30, (right) and Callum Robinson, 33, (centre left; pictured with their parents) vanished without a trace in the Baja California region in Mexico

The brothers were traveling with 30-year-old American Jack Carter Rhoad (pictured here in an image uploaded by Callum last Saturday). Four bodies were found on Friday

Baja California state Attorney-General Maria Elena Andrade Ramirez said a murder investigation had commenced and indicated investigators believe the three men were killed in an attempted robbery.

'When they tried to get the vehicle, the victims opposed the robbery, the robbers were armed with a firearm and apparently shot the victims,' she told 7News.

Shell casings were found at the campsite were the three men were last seen, a surfing spot known as La Bocana at Santo Tomas, local media reported.

Prosecutors have confirmed three people - two brothers and a 23-year-old woman - who were arrested earlier this week have now been charged with a crime equivalent to kidnapping on Friday.

Forensic tests will be undertaken by the local laboratory to identify if the bodies are the missing trio, the Baja California prosecutor's office said in a statement. 

The remains were found in a well more than 15 meters (49ft) deep next to a cliff at Punta San José in Santo Tomás, in the municipality of Ensenada, near a remote surfing spot known as Lighthouse, reports the San Diego Union-Tribune.

It took rescuers about 20 hours to pull the bodies out of the well.

The Perth brothers and their San Diegan surfing buddy were on holiday in Ensenada, about an hour and a half south of the U.S.-Mexico border, when they vanished.

Before the discovery of the bodies, local police had suspected foul play as Jack Rhoad's burned-out truck was found as well as an abandoned campsite with traces of blood and 'dental parts', reported Zeta.

Australia's 7News has also reported a tooth was discovered.

The remains were found in a well more than 15 meters (49ft) deep next to a cliff at Punta San José in Santo Tomás, in the municipality of Ensenada

The well is near a remote surfing spot known as Lighthouse (the recovery operation is seen)

Rescue workers are pictured at a crime scene where human remains were found near La Bocana Beach in Ensenada

Hours before the remains were found, Australian media reported Callum and Jake's parents were flying out to Mexico to look for their missing sons. It is unclear if they made it on a flight before police announced the discovery of the bodies.

It comes after the three young men shared eerie final social media posts from their trip, where they were seen having the time of their lives on the beach.

Baja California, where the men shared their vacation snaps, is known as one of Mexico's most violent, cartel-controlled states.

The disappearance of the men has not been linked to organised crime, but investigators are not ruling anything out.

Investigators continue to search the rugged area where the bodies were found for additional evidence, the prosecutor's office said. 

Hours before the bodies were found, Australian media reported Callum (right) and Jake's (left) parents (pictured) were flying out to Mexico to look for their missing sons

It comes after the three young men shared eerie final social media posts from their trip, where they were seen having the time of their lives on the beach 

Police believe the trio's vehicle was later found burnt-out in the Santo Tomás area 

A woman and two men, all Mexican, have been arrested in connection to the case, Baja California Attorney General María Elena Andrade Ramírez (centre) told reporters

Mexican officials are seen in a checkpoint in Ensenada on Thursday

Ramirez has not said if the arrested parties were believed to be involved in the men's disappearance, and insisted before the bodies were found that 'all lines of investigation are open'.

In social media posts shared by Callum just before they vanished, the trio was seen relaxing at Rosarito Beach, where they were said to be surfing and camping as they moved up and down Mexico's west coast.

They reportedly planned to move on to Ensenada, about 50 miles (80km) down the coast, but concerns were raised when they failed to check into an Airbnb on Sunday.

The last image posted to Callum's Instagram showed the group had made it to San Miguel beach in Ensenada before vanishing without a trace.

One chilling picture showed their white Chevrolet Colorado pickup truck at a beach in Rosarito, which police believe was the same vehicle later discovered burned out. 

'... and it begins,' Callum had captioned an image of the truck at the beach, alongside an emoji of the Mexican flag, at the start of the trio's doomed trip.

The Robinson brothers had attended Coachella before going to Mexico to surf.

Callum was based in the U.S. where he was an accomplished lacrosse player known  as 'the Big Koala', and Jake, who worked in regional hospitals across Australia, had flown out to San Diego two weeks ago to visit him.

Rhoad worked in technology services in San Diego.

While the bodies are yet to be formally identified, Callum's college team Stevenson University Lacrosse claimed in a social media post he had been killed.

'It is with heavy hearts that we share the news of the passing of our dear teammate and friend, Callum Robinson,' the club said.

'From his days leading us to victory on the field to his unwavering commitment to academic excellence, Callum was a true inspiration to us all.

One chilling picture shows a white Chevrolet Colorado pickup truck at the beach in Rosarito 

The men are understood to have gone missing from the Baja California region near Ensenada

Callum documented the trip on Instagram before going silent a week ago 

'But, beyond his accolades, Callum will be remembered for his infectious spirit and larger-than-life personality.

'With his beautiful long hair and charming smile, he truly embodied the nickname 'big koala' - warm, friendly, and always there to lend a helping hand.

'Though he may be gone, Callum's legacy will live on in our hearts forever.

'Our thoughts and prayers are with his family and loved ones during this difficult time. Rest easy, Callum. You will be deeply missed, but never forgotten.'

In an Instagram post, his teammate Will Manny thanked Callum for 'showing everyone how to smile big, laugh hard and enjoy life'.

'Callum Robinson, Jake Robinson and Jack Rhoad, rest in peace. And to your families, the lacrosse community is here for you,' he said.

Brett Hiken described the young player as 'one of one', adding that he was lucky to have 'gotten to love and know' him.

'You made everyone feel like family and everyone was your best friend,' he said.

'Our best memories were always with you. Truth is, everyone wanted to be like you but no one was even on the same planet.

'It was a honor to get be your friend. The room turned every time you entered without even opening your mouth.

'Love you like the brother you are and most importantly thank you. Everyone gets to live, but man not everyone truly lives. You certainly lived.'

Callum has been called an 'Australian lacrosse star' who moved to San Diego with the aim of playing professionally

The Robinson brothers attended Coachella before going to Mexico to surf. Callum was based in the U.S. where he was a lacrosse player known as 'the Big Koala', and Jake, who worked in regional hospitals across Australia, had flown out two weeks ago to visit him

Teammates have shared tributes to talented and popular athlete

Police also say they found three abandoned tents south of Ensenada, with local media reporting that blood was found on them.

The trio had been actively sharing images of their trip right up until they failed to show up at their Airbnb.

It is understood police were able to make the arrests after one of the brothers' mobile phones was turned back on, and pinged a local mobile tower.

'A working team [of investigators] is at the site where they were last seen, where tents and other evidence was found that could be linked to these three people we have under investigation,' prosecutor Andrade Ramírez said in a statement before the bodies were found. 

Ramírez said her office was in contact with Australian and U.S. officials but suggested it would be difficult to find the men given the time that had already passed.

'Unfortunately, it wasn't until the last few days that they were reported missing. So that meant that important hours or time was lost,' she said.

Baja California has been plagued by cartel violence in recent months. 

In 2015, two Australian surfers, Adam Coleman and Dean Lucas, were killed in western Sinaloa state, across the Gulf of California, also known as the Sea of Cortez, from the Baja peninsula. 

Authorities say they were victims of highway bandits. Three suspects were arrested in that case.

Debra Robinson appealed for help from the public in the search for her sons on Thursday, the day before three bodies feared to belong to the men were found  

The mother of the Robinson brothers, Debra Robinson, spoke of her anguish after her sons vanished, as she appealed for help before the bodies were found. 

She stressed Callum was a diabetic as she asked anyone with information to come forward.

Debra wrote on social media: 'Australian friends Jake and Callum Robinson have gone missing around Rosarito/Ensenada region of Baja California Norte Saturday morning.

'They were likely surfing. Callum is diabetic - this is a very dire situation.'