Brazil's G1 news portal says Attorney General Rodrigo Janot has asked the Brazilian Supreme Court to authorize investigations of former President Luiz Inacio Lula da Silva over alleged involvement in corruption at state-owned oil company Petrobras.

The attorney general's office and the Supreme Court said they could not confirm the report on the news site of Brazil's biggest TV network, Globo.

G1 says the attorney general also wants to investigate Social Communications Minister Edinho Silva, Political Affairs Minister Ricardo Berzoini and Jaques Wagner, who heads the office of President Dilma Rousseff.

The report comes a day after the attorney general asked Brazil's highest court to authorize an investigation of opposition presidential candidate Aecio Neves for alleged involvement in the Petrobras bribery scheme. Neves narrowly lost the 2014 election to Rousseff.