Brazil's attorney general has asked the country's highest court to authorize an investigation into embattled President Dilma Rousseff over obstruction of justice allegations, according to major Brazilian news organizations.

The country's top newspapers and the Globo television network said late Tuesday that Rousseff was among 30 people targeted by Attorney General Rodrigo Janot's requests. Others included ex-President Luiz Inacio Lula da Silva and Solicitor General Jose Eduardo Cardozo, as well as opposition politician Aecio Neves, who lost to Rousseff in the 2014 presidential race, and House Speaker Eduardo Cunha.

A spokeswoman at the attorney general's office told The Associated Press on Wednesday that the agency was not commenting.

Janot's request adds to problems buffeting Rousseff. The Senate looks likely to vote next week to suspend her and move forward with impeachment. If that happens, Vice President Michel Temer would take over for six months or until the conclusion of the impeachment trial.

The media reports say Rousseff is suspected of trying to undermine the snowballing investigation into corruption at the state-run oil company Petrobras by appointing her predecessor, Silva, as her chief of staff this year. Silva's nomination was later suspended.

Rio de Janeiro's O Globo newspaper reported that Janot's request accuses Silva of being the ringleader behind the massive scheme that saw top construction firms pay bribes in exchange for inflated contracts with Petrobras, with some of the money ending up in the coffers of political parties from across the ideological spectrum. The case has already ensnared leading politicians and businessmen.

"This criminal organization could never had functioned for so many years and in such a wide and aggressive manner within the federal government without ex-President Lula's taking part in it," the newspaper quoted Janot's petition as saying.

The reports say the requests grew out of the plea bargain testimony by Sen. Delcidio do Amaral, formerly the government's leader in the Senate. who was detained after recordings emerged suggesting he was plotting to spirit a key player in the Petrobras scandal out of the country.

Silva and Rousseff have repeatedly denied any wrongdoing.

Rousseff on Wednesday cast doubt on Amaral's testimony, saying the senator "is in the habit of lying." She added that the leaked news of Janot's requests appeared to have been timed to do maximum damage to her and her close collaborators.

The Senate's impeachment commission was expected to vote this week on whether to recommend impeaching Rousseff, with the decisive vote by the full Senate slated for next Wednesday.

Teori Zavascki, the Supreme Court justice in charge of the Petrobras investigation will decide whether to honor Janot's requests, though the news reports say there is no timetable for a decision.