Krzysztof Chmielewski (l) and Holger Hagenbusch had spent years travelling the world on bikes
Mexican investigators say two European cyclists did not die in an accident as first claimed - they were murdered.
The bodies of Holger Hagenbusch, from Germany, and Krzysztof Chmielewski, from Poland, were found at the bottom of a cliff in Chiapas state.
Local authorities had said the pair appeared to have fallen after losing control.
However, relatives and fellow cyclists suspected it was more sinister, and had called for a deeper investigation.
The newly appointed special prosecutor, Luis Alberto Sánchez, said, on Friday, that they were killed in what appears to have been a robbery.
"Our investigations up to now indicate this was an intentional homicide," he said.
Chmielewski's body was found first, 40 metres below the road, on 26 April.
Hagenbusch was found eight days later - on 4 May - further down the ravine, but beneath the same road that runs between Ocosingo and San Cristóbal de las Casas in the country's far south.
The regional attorney general in Chiapas, Arturo Pablo Lievano, originally said there was no evidence of bad intent and everything pointed to an accident. He said they may have been run off the road by a vehicle.
However, Hagenbusch's brother, Reiner, told the German press he believed they had been killed and there had been some sort of attempted cover-up.
After travelling to Mexico to identify his brother's body, he also found out information about the Polish biker.
"The Polish cyclist was decapitated and had a foot missing," he wrote on Facebook.
investigators now believe that the pair were assaulted on either the 19 or 20 April.
Chmielewski sustained a head injury that may be a gunshot wound, said Mr Sánchez.
His body was found next to a bike - but it was not his own. It belonged to his German companion, which aroused suspicions.
Talking to BBC Mundo, Mr Sánchez said the assailants were probably trying to cover their tracks. "Those that did this wanted to make it appear like an accident, so they put the bike there, but they made a mistake and used the German's bike," he said.