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BRASILIA, April 15 (Reuters) - Brazilian police arrested another four people in the political kickback investigation engulfing state-run oil company Petrobras on Wednesday and local media said they included Joao Vaccari, the treasurer of the ruling Workers' Party.
Vaccari is the closest political figure to President Dilma Rousseff so far implicated in the Petrobras scandal which has thrown her government into crisis at the start of her second term.
Federal police said they carried out four arrest warrants in Sao Paulo early on Wednesday and the detainees were being taken to Curitiba where the investigation into the so-called Car Wash operation is centered.
The Globo and Folha newspapers reported online that Vaccari was picked up at his home in Sao Paulo as part of the new wave of arrests.
Former Petrobras executives at the center of the corruption investigation have said in plea bargains that Vaccari received more than $200 million in graft money skimmed off overpriced construction and engineering contracts.
Vaccari denied the accusations last week before a congressional inquiry commission. He said all campaign donations to the Workers' Party from the construction and engineering companies were legal and registered with electoral authorities.
Some leading members of the Workers' Party have called for Vaccari's resignation, but Vaccari and the party have insisted on his innocence.
Prosecutors are investigating 47 politicians, all but one of them from Rousseff's ruling coalition, for allegedly receiving funds from the graft scheme at Petroleo Brasileiro SA , as the oil company is formally known.
So far, 97 people have been indicted on charges of corruption, forming a cartel and money laundering. They include four former senior managers of Petrobras and dozens of executives from Brazil's biggest construction and engineering firms. (Reporting by Anthony Boadle Editing by W Simon)