Mexican authorities are investigating reports of clandestine grave sites in the hamlet of Carrizalillo, near a gold mine operated by a Canadian company.

The Attorney General's Office said forensics experts and police had been sent to the sites in southern Guerrero state, but did not say what they found.

But inhabitants say at least three pits with human bones have been found. On Wednesday, they showed reporters what appeared to be hip or leg bones in the pits.

Three employees of a mine operated by Canada's Goldcorp were kidnapped and killed in the area in March. Their bodies were found. But Figueroa said inhabitants reported seeing pickup trucks full of bodies heading out to the rural area last year.

The Guerreros Unidos drug gang has been active in the area.