Human remains believed to be those of the "Pebco Three", who were murdered by apartheid-era police, were found on a farm near Cradock, the National Prosecuting Authority (NPA) said on Monday.

Spokesperson Panyaza Lesufi said NPA investigators followed up several leads and discovered the remains during a dig on the Cradock farm known as Post Chalmers that previously belonged to the police.

The Pebco Three - Sipho Hashe, Qaqawuli Godolozi and Champion Galela - were kidnapped at the Port Elizabeth airport in 1985 by security police and subsequently murdered on the farm.

In 1999 the Truth and Reconciliation Commission (TRC) refused four security police officers amnesty for their involvement in the crime.

The amnesty applications of Herman Barend du Plessis, Johannes Martin van Zyl, Gideon Nieuwoudt and Gerhardus Johannes Lotz were heard in Port Elizabeth in 1997.

The widows of the victims opposed the amnesty applications, saying there had not been full disclosure.

The four told the TRC that they burned the bodies of the murdered activists and thrown the remains into the Fish River.

Lesufi said he hoped that the discovery would force the remaining officers - Nieuwoudt has since died - to come forward and assist the NPA.

He said forensic investigations were continuing to establish whether the remains were definitely those of the three.

Lesufi said the NPA believes that if the remains were not those of the Pebco Three they might be those of other activists.

During the TRC hearings the applicants claimed the three leaders had to be killed because they posed a danger to the state through their involvement in the underground operation of the African National Congress in Port Elizabeth.

The TRC said it had refused amnesty to Van Zyl, Nieuwoudt and Lotz for in the Pebco Three case because they had failed to make full disclosure.

Du Plessis was refused amnesty for ordering the kidnapping and murder of the three deceased and for conspiring to murder them.

Another security police officer, Gerhardus Cornelius Beeslaar, was refused amnesty for kidnapping and assaulting Hashe.

Amnesty was also refused to Johannes Koole for the kidnapping of the Pebco Three and the assault on Hashe and Godolozi.

The only senior security force officer to be granted amnesty in the case was former Port Elizabeth security force head Harold Snyman. Snyman has since died.

Kimani Peter Mogoai, an askari (a member of the liberation movement who changed sides to work for the apartheid state), was granted amnesty for the kidnapping of the three leaders and the assault on Hashe and Godolozi.

- Pebco was the acronym for Port Elizabeth Black Civic Organisation. - Sapa