Mexican authorities say three bodies thrown down a well in Baja California state are likely those of two Australian brothers and a US friend who may have been victims of a bungled robbery.

Regional officials confirmed the bodies were located on a cliff top in the Baja Peninsula, on Mexico’s west coast, on Saturday.

Forensic tests will be undertaken by the local laboratory to identify if the bodies are missing Perth siblings Callum and Jake Robinson, the Baja California prosecutor’s office said in a statement.

“All three bodies meet the characteristics to assume with a high degree of probability that they are the American Carter Rhoad as well as the Robinson brothers from Australia,” Baja California’s state Attorney-General María Elena Andrade said on Saturday.

She said while the three bodies were found in an advanced state of decomposition at the bottom of a well more than 15m deep, “some physical descriptions give us that high probability”.

Mexican authorities’ preliminary hypothesis is that the arrested individuals attempted to carjack the foreigners and when the surfers resisted they were shot, with their bodies dumped in a well, Andrade said.

A fourth body was discovered in the well although that corpse had been there for longer and is not believed to be linked to this case, Andrade said.

Baja California prosecutors on Thursday said they were questioning three people over the case.

On Saturday authorities said a criminal charge of forced disappearance, equivalent to kidnapping, had been laid against one of the three.

Investigators also found a burnt-out white ute, believed to be the vehicle in which the men were travelling when they disappeared.

The chief state prosecutor’s office said evidence found along with abandoned tents at a burnt-out campsite was linked to the three people being questioned about the missing foreigners.

Local news outlet Zeta reported the fourth body found in the well was believed to be that of the property’s owner, who has been missing for several weeks.

The Robinson brothers, both in their 30s, were travelling in the region on a surfing holiday when they failed to check into pre-arranged accommodation near the city of Ensenada.

Their mother Debra Robinson appealed for help to find her two sons and their US friend Rhoad, saying she had not heard from them since Saturday.

“Callum is a type one diabetic so there is also a medical concern,” she wrote on Mexican social media.

Officials from the Department of Foreign Affairs and Trade said it was obviously a distressing time for the family but the agency was in constant contact.

Foreign Affairs Minister Penny Wong reiterated that the government was doing everything it could to support the family

“I can indicate that our embassy in Mexico, as well as the Australian Federal Police, are working in support of local authorities, that my department is providing consular support to the families concerned,” she told reporters on Saturday.

Health Minister Mark Butler said the department was trying to glean as much information as possible from Mexican authorities to inform the family.

“This is deeply distressing to the Australian community, particularly the family and friends of these two young Australians” he told reporters on Saturday.

The brothers’ family is understood to be travelling from Perth to Mexico to be closer to the investigation, Nine Network reported.

The US State Department is also monitoring the investigation.

Both US and Australian authorities have urged people to exercise a high degree of caution when travelling to Baja California “due to the threat of violent crime”.

with Reuters and AP

By Savannah Meacham and Jacob Shteyman in Canberra