Brazilian prosecutors filed corruption charges on Monday against the treasurer of the ruling Workers' Party (PT), further implicating the government in the massive Petrobras oil scandal that has already involved former presidents and lawmakers.

João Vaccari was among 27 individuals reported by the Federal Public Ministry for corruption, money laundering and conspiracy. Prosecutors said they have “ample proof” that Vaccari solicited bribes from Renato Duque, a former Petrobras official, accused of laundering money from the company, the Guardian reported.

Another former Petrobras official, Pedro Barusco, who was also charged in the sting, testified that he had met Vaccari to discuss exchanging bribes for favorable contractors. “Vaccari knew that the payments were actually bribes,” Deltan Dallagnol, a prosecutor in the investigation, told reporters, according the New York Times.

Duque was arrested at his Rio de Janeiro house on Monday. Prosecutors issued an arrest warrant after discovering transfers of about 20 million euros ($21 million) between offshore accounts held in Switzerland and Monaco, amounts which were “not compatible” with his earnings at Petrobras.

The PT had allegedly received as much as $200 million in bribes, some of which was used to fund the election campaign of President Dilma Rousseff. The party said all of its funds were legitimate and denied any knowledge of the bribes.

Operation Car Wash, as the investigation into Petrobras is known, has already implicated dozens of top political figures, including a former president and current leaders of Congress. Prosecutors allege that executives and construction companies had been skimming funds and accepting kickbacks for favorable contracts, funneling the money into various political parties.

Rousseff is not being investigated despite serving as the chair of Petrobras’ board at the time when the kickbacks took place, but there have been growing calls to impeach her government. Over 1 million Brazilians took to the streets on Sunday to demand Rousseff's impeachment, protesting the country’s flagging economy and the ongoing scandals just three months into her second term.

In a Sunday address, Rousseff asked for “patience,” stressing that the country’s economic troubles were short term. “We’re going through temporary problems, but our fundamentals continue strong,” she said.