Investigations ordered into dozens of politicians linked to a massive corruption scandal at state oil giant Petrobras is sending shock waves through Brazil's governing coalition and South America's largest economy. After a day of high suspense, Brazil's Supreme Court on Friday greenlighted investigations into a who's who of the country's politics. The list encompasses 49 politicians, headed by the Senate president, Renan Calheiros, and Speaker of the Chamber of Deputies Eduardo Cunha, both leaders of the centrist Brazilian Democratic Movement Party, or PMDB, which is a key component of President Dilma Rousseff's ruling coalition. The PMDB has emerged from the scandal weakened and divided, with some members reaching out to the opposition, weakening Rousseff's hold over Congress at a time when the country faces major challenges to its faltering economy. Private contractors are alleged to have paid huge bribes to gain inflated Petrobras contracts, and then funneled payments to senior politicians. The loss to Brazil's largest corporation has been estimated at US$3.8 billion. Among those named in the sprawling Petrobras corruption probe are 12 senators and 22 deputies from five parties, including three in the ruling coalition. Rousseff is not being investigated, even though she chaired the Petrobras board for much of the decade when the corruption is alleged to have flourished. On Saturday, Justice Minister Jose Eduardo Cardozo stressed that nothing found so far had warranted an investigation of the president, correcting "erroneous" press reports that prosecutors had held off because she enjoyed immunity. "There was nothing rejected in regard to the president, since there were neither deeds nor evidence against her" in the investigation, he said. But prosecutors will investigate the financing of Rousseff's 2010 presidential campaign, when she succeeded her mentor President Luiz Inacio da Silva. Antonio Palocci, Lula's former finance minister and Rousseff's former chief of staff in 2011, is reported to be cooperating with investigators in hopes of obtaining a reduced sentence.