South African authorities have unearthed a mass grave that they believe contains the bodies of African National Congress militants killed more than 20 years ago.

A total of 21 bodies have been found in the mass grave outside the town of Rustenberg - about 100 kilometers northwest of Johannesburg. Authorities believe the site was a pauper graveyard, and they say most of the bodies show no signs of foul play.

But they say at least four of the bodies had multiple bullet wounds - suggesting they may be the remains of missing ANC militants killed in clashes with security forces in the area during 1985 and 1986. The remains are undergoing forensic examination to determine their identity and cause of death.

South Africa's National Prosecuting Authority has been working to locate the remains of hundreds of activists who disappeared during the apartheid era.