MEXICO CITY (AP) — Volunteer searchers found two sets of skeletal remains and heaps of burned bone fragments in what they called a clandestine body disposal site in the desert of the northern border state of Sonora.

They did not say how many bodies had been found. On Monday, state prosecutors said the bones were probably from three to four people.

The searchers are mainly mothers looking for their disappeared children.

The “Searching Mothers” of Sonora volunteers called the site in Santa Ana, Sonora an “extermination camp,” and posted videos of craniums and pieces of bone and clothing they had dug from pits.

Sonora has been the scene of bloody turf battles between drug cartels.

Mexico has more than 95,000 disappeared, according to government data. More than 93,000 of those disappearances occurred since 2006, when the government began its war against organized crime. Most are thought to have been killed by drug cartels, their bodies dumped into shallow graves, burned or dissolved.

The government has struggled to identify even the bodies that have been found. Some 52,000 await identification.