(Adds details from police press conference)
BRASILIA, July 4 (Reuters) - Brazil's federal police served five arrest warrants and conducted search and seizure operations in three states on Monday, in the latest round of a sweeping corruption probe around state-run oil firm Petroleo Brasileiro SA.
Police said contractors paid at least 39 million reais ($11.99 million) in bribes to executives of Petrobras, as the oil company is known, and rigged public auctions at Petrobras' research center Cenpes.
Part of the funds allegedly embezzled were directed to the leftist Workers Party, the ruling party in Brazil from 2003 to May 2016.
The party's former treasurer, Paulo Ferreira, was already in custody for a separate probe but now faces another arrest warrant for his alleged role in the Petrobras fraud, police said at a press conference.
Representatives for the Workers Party and Ferreira were not immediately available to comment.
No arrest warrants were issued against sitting politicians for the Monday raids, the 31st round of the two-year-long "Operation Car Wash." The investigation, which has rocked Brazil and led to the arrests of dozens of political and corporate leaders, uncovered a deeply-rooted corruption and price-fixing scheme at Petrobras and other state-led companies.
Though politicians from various of Brazil's biggest parties have been ensnared in the probe, the fallout from the scandal helped topple the Workers Party because it undermined much of the popular and legislative support for Dilma Rousseff, who was suspended as president in May.
Rousseff, who faces impeachment proceedings in Brazil's Senate over allegations of irregularities in the government budget, was replaced by interim President Michel Temer, a centrist and veteran legislator who was her vice president.
$1 = 3.2532 Brazilian reais Reporting by Silvio Cascione; Editing by Andrew Heavens and Frances Kerry