SAO PAULO (Reuters) - Brazilian federal police summoned João Vaccari Neto, the treasurer for the country's ruling political party, for questioning in a corruption probe focused on state-run oil company Petrobras on Thursday, as the investigation broadens to include political operators.
"We want to know about donations that he solicited, legal or illegal, from people who had contracts with Petrobras," prosecutor Carlos Fernando dos Santos Lima said at a press conference in Curitiba, where the probe is based.
Police and prosecutors have found evidence that former Petrobras executives and firms that had contracts with the company funneled kickback payments to President Dilma Rousseff's Workers' Party and its allies in Congress.
The probe has ballooned into Brazil's biggest-ever corruption scandal over the past year, leading to the arrest of executives at the country's top engineering firms and on Wednesday triggering the resignation of the chief executive and other senior management at Petrobras.
A federal police statement said four additional arrest warrants had been served on Thursday and 18 people had been called to testify. Prosecutors said Vaccari, who has not yet been charged with any crime, was among those summoned.
The latest phase of the investigation identified 11 new suspects, including Vaccari, who may have delivered funds stolen from Petrobras and the engineering firms to politicians and party operators. The scheme appears to have continued into 2014, Lima said.
As treasurer for the party, Vaccari was responsible for soliciting campaign donations for Rousseff during last year's presidential election. A press spokeswoman for the Workers' Party in Brasilia said the party had no comment.
Rousseff has denied any knowledge of the scheme and urged a thorough investigation, but the probe has become a major headache for her as she chaired the board of Petroleo Brasileiro SA, as the company is formally known, between 2003 and 2010 when much of the alleged graft took place.
Police said some 200 officers are involved in the latest phase of the operation in the states of Sao Paulo, Rio de Janeiro, Bahia and Santa Catarina.
The investigation is based in Curitiba, where the first money-mover in the scheme was discovered. The Supreme Court in Brasilia, the only court where politicians can be tried under Brazilian law, is expected to open a case involving politicians after the carnival holiday later this month.
(Reporting by Walter Brandimarte, Caroline Stauffer and Gustavo Bonato Editing by W Simon)