Authorities are investigating a mass grave in southern Mexico, the 167 bodies were dumped there contain at least 50 years, said a Mexican official Saturday.
The remains in a cave near the border with Guatemala found "disintegrate on contact," the official said the prosecutor of the State of Chiapas.
Researchers are trying to determine the age and sex of the victim and the cause of death, the official said on condition of anonymity.
Close to the advanced state of decay that at least 50 years, he said, adding that there were no obvious signs of violence.
A 36-year civil war in Guatemala, which began in 1960 claimed 250,000 dead and missing 45,000. Activists suspect that they were killed by soldiers and buried in secret.
In recent years, drug gangs, the bodies of hundreds of victims, including dozens of Central American migrants in mass graves down.