Four men accused of crimes against humanity during Argentina's dictatorship have decided to break a pact of silence among ex-members of the military who are on trial and collaborate with authorities in identifying victims and burial sites, a judge said Wednesday.

Presiding judge Diaz Gavier said the four former soldiers had "voluntarily expressed their intention to provide information that will facilitate the location of some human remains."

The four are being tried for their alleged participation in crimes committed at clandestine detention centers in Cordoba province during the South American country's 1976-1983 dictatorship.

In a hearing Wednesday, Ernesto Barreiro, a former officer who human rights groups say was the chief torturer at the La Perla detention center, indicated places where 25 people listed as missing might have been buried.

"The accused in these cases have never before expressed their willingness to collaborate in clarifying events, which implies a major change in the position from what we have historically seen," Gavier said, referring to the refusal by ex-security force members to give details of alleged killings and disappearances during trials.

In 1987, during the elected government of President Raul Alfonsin, Barreiro was a leader of a 1987 military rebellion that forced Argentina to pass an amnesty law for accused human rights abusers. The amnesty law was overturned almost two decades later, allowing prosecutors to reopen hundreds of cases.

President Cristina Fernandez called Barreiro's revelations "an achievement for Argentine society" and said the sites mentioned will be inspected by forensic anthropologists.

Human rights groups say about 30,000 people died or disappeared in Argentina's brutal dictatorship.