SAO PAULO, Brazil (AP) _ Authorities on Tuesday uncovered a clandestine mass grave containing the remains of an estimated 1,700 bodies - mostly poor people but also some political foes of Brazil's former military dictatorship.

The skeletons were packed in blue plastic bags and buried in an unmarked section of the hillside cemetery of Perus, a working-class suburb of Sao Paulo, the country's largest city.

Officials found the bones while checking up on what had happened to remains of paupers who died with no identification in the early 1970s.

''Up to 50 of the dead could be former political prisoners and opponents of the (1964-85) military regime,'' Luis Eduardo Greenhalgh, deputy mayor of Sao Paulo and a human rights activist, told The Associated Press.

He said at least six already had been identified as ''disappeared'' political activists, presumably killed by the dictatorship.

Greenhalgh said others may have been victims of police-backed death squads that summarily executed suspected criminals in the 1960s and '70s.

Cemetery director Antonio Pires Eustaquio said most of the dead were paupers buried in 1971-72, whose identities were unknown at the time.

By law, such remains must be unearthed and placed in a bone depository after three years, Eustaquio said.

He said, ''Cemetery records showed the removal took place but did not indicate what had been done with the remains. I investigated and discovered the mass grave.''