The Brazilian attorney general's office launched an investigation Monday into five retired soldiers accused of torturing and killing a congressman during the country's 1964-1985 military dictatorship.

Brazil has never jailed any of those responsible for the military regime's abuses, mainly because of a 1979 amnesty law, but a judge last week in a separate case paved the way for Monday's action.

Rubens Paiva, a civil-engineer-turned-politician who was critical of the regime, was arrested at his home in January 1971 and taken to the offices of a military intelligence unit where he was tortured to death, the attorney general's Rio de Janeiro office said on its website.

The five then-soldiers -- who are all still alive -- are accused of killing him, hiding his body and concocting a story that he had escaped.

Investigators said the accusations were based on documents found at the home of Paulo Malhaes, a retired colonel who was found dead last month after admitting to torturing political prisoners during the dictatorship.

Malhaes' death, still under investigation, came a month after he told Brazil's National Truth Commission that Paiva's body had been thrown into a river after he was tortured to death.

Civilian judge Ana Paula Vieira de Carvalho ruled last week in a separate case that crimes against humanity were not covered by the 1979 amnesty law and ordered five former army officers to stand trial over a 1981 bombing targeting a Labor Day concert.

The attorney general's office echoed that argument in launching criminal proceedings against the five retired soldiers Monday.

"The crimes committed by these soldiers happened in the context of a systematic and generalized attack on the civilian population by a semi-clandestine system of political repression," the office said in a statement.

The junta's agents were guilty of the "kidnap, torture and disappearance of enemies of the regime," and were therefore not covered by the amnesty, it said.

If convicted, the ex-soldiers face prison and could lose their pensions, as well as any military honors they have received.

The attorney general's office said its investigations indicated the Brazilian army had been hiding information about its soldiers' roles in dictatorship-era crimes and that it was requesting a judicial order to make the military hand over the soldiers' complete files.