The discovery of a clandestine mass grave containing more than 1,700 bodies, some apparently of political opponents of Brazil's former military rulers, has stirred many painful memories. Although an amnesty passed by the former military dictatorship bars trying anyone for involvment in the deaths, activists are demanding a full investigation. ``The construction of a state of law and democracy demands the truth ... is fully told,'' said a statement issued last week by two human rights groups. ``This necessity is even greater in Brazil because the amnesty eliminated the possibility that those responsible for torture and assassinations would be held accountable for their actions,'' the statement said. The grave, discovered Tuesday in Perus on the outskirts of Sao Paulo, contained mostly the remains of paupers. But an estimated 50 of the dead are believed to be former enemies of the military government that ruled from 1964 to 1985. Some of the skeletons unearthed had damaged skulls from gunshot wounds to the head, and human rights officials say the people were summarily executed. A pacemaker and platinum dental work also indicated that not all the remains were those of paupers. Sao Paulo Mayor Luiza Erundina said records at three other city graveyards would be checked this week to see if other military ``enemies'' were buried there. Unlike some South American countries, Brazil never fully investigated human rights abuses that occurred under military rule. In Argentina, a full public accounting of the crimes of the 1976-1982 dictatorship took place. Five former junta members later were found guilty of murder and human rights violations. Uruguay returned to civilian rule in 1985 after nine years of military dictatorship. A nationwide referendum was held there on revoking the military's self-approved amnesty, and after much public debate the amnesty was narrowly upheld. Brazil's dictatorship was not as brutal as some in the region, but it systematically violated human rights. Rights groups say about 200 people were killed in Brazil, 150 disappeared and thousands were tortured. Many people with leftist sympathies were exiled. However, a key to the 1985 return of civilian rule, which was negotiated among the generals and civilian politicians, was the understanding there would be no investigations or trials of former military officials. ``That agreement allowed the civilians to take charge and provided them with some stability,'' said political science professor David Fleischer, who worked in Brazil's Senate during the transition period. ``But it also had a negative side: The military maintained great influence, and there was no definitive rupture with the past,'' he said. One direct result was that hundreds of those directly involved in torture and human rights violations retained their positions in the police and armed forces. President Fernando Collor de Mello, who took office in March as Brazil's first directly elected president since 1960, promised to abolish the National Intelligence Service, the former dictatorship's secret police force, which was involved in repression of civilians. Instead, he renamed the agency and put a civilian in charge, but it continues to spy on the population. Some people hope the discovery of the mass grave leads to a renewed interest in fully airing abuses committed during the military rule. ``The truth is a moral sanction,'' wrote prominent political columnist Clovis Rossi in the Folha de Sao Paulo newspaper. ``The widows, the orphans and the brothers and sisters of the victims have the right to know who killed their loved ones.''