Police in Mexico have discovered dozens more bodies in an abandoned silver mine suspected of being used by drug gangs to dump their victims.

The first 20 corpses were pulled out more than a week ago from the bottom of a 150-metre deep shaft at the Concha mine in the town of Taxco in Mexico's southern state of Guerrero, the state attorney-general's office said on Monday.

Investigators have been rappelling into the mine shafts to look for bodies since the first ones were found on May 29, and have 10 more ducts to explore.

Some of the 55 bodies pulled out of the mine by Saturday were already in advanced stages of decomposition, police officials said in a statement.

"The smell was intolerable," said Carlos Amezcua, the head of emergency services in Guerrero who participated in the recovery effort.

Among the dead was a recently kidnapped prison director, although the majority of victims of have not been identified.

Identifying bodies

Forensic examiners are trying to determine whether other human remains, clothing and shoes found in the shaft correspond to the bodies already found.

Authorities were tipped off about the mass grave in late May after they arrested an organised crime suspect in the nearby city of Iguala.

Nearly 23,000 people have died in drug-related violence since Felipe Calderon, the Mexican president, launched an army-led crackdown on drug gangs soon after he took office in late 2006.

Most have been killed in clashes between rival cartels fighting for drug smuggling routes to the United States, the No 1 consumer of Mexican narcotics.