Mexican authorities pulled out at least 19 bodies from a deep canyon in Guerrero, the state that frequently suffers from drug cartel violence.
The bodies were discovered between December 8 and 11 in the village of Chichihualco.
"There were nine complete bodies and eight half-burned" an official said.
Two more bodies were also found in pieces.
The identities, ages or even genders of the victims are not known.
When exactly they were dumped into the 500 m depth (1,650-foot) canyon is also not known. Authorities said that it appears to be between a month and a year and a half ago.
Mario Vergara, head of The Other Disappeared, an organisation that searches for missing people in Guerrero, told AFP that an American who was searching for a missing relative encountered the bodies.
"He says that he had to pretend to be a farmer to go unnoticed because it's an area where marijuana is grown. He bought goats to go through the hills," Vergara said, noting that the man eventually gained the trust of locals.
"The bodies were not buried. They were on the ground. There were bodies hanging from trees. I'm told it was like hell," he said.
Isabel Rosales from another organisation of relatives of missing people, said the bodies were sent to Mexico City to be identified.
Rosales said members of the Committee of Relatives and Friends of Kidnapped, Missing and Murdered People of Guerrero asked the attorney general's office to take their DNA samples to match with the remains found.
There are 45 missing cases of the committee throughout Guerrero which was found in 2007.
Guerrero is one of the most violent states of Mexico, where over a dozen drug gangs fight control over poppy production and other criminal activities.
The 43 missing college students have also disappeared in Guerrero last year in September.
There are some 26,000 missing and tens of thousands of dead people in Mexico.