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Brasilia (Reuters) - Brazil’s former President Luiz Inacio Lula da Silva had “complete knowledge” of the massive political kickback scheme that centred on contracts at state-run oil firm Petrobras, a former top executive testified on Friday.

Former Petrobras engineering and services director Renato Duque, testifying in the first of five corruption trials Lula faces, told a federal judge that Lula had “command” of the scheme.

But Duque, convicted on corruption charges in four separate trials for taking bribes in the Petrobras scheme and sentenced to more than 56 years in prison, emphasized during his testimony that he was seeking a plea-bargin deal that would reduce his time in prison.

“I would like to make clear my intention here is to act as a collaborator, to tell the truth, to clarify what is possible and within my reach in this case and any others you think necessary,” Duque told Judge Sergio Moro, who has spearheaded the anti-corruption drive.

Lula’s lawyers did not immediately respond to a request for comment on Friday, but they have repeatedly said the former leader is innocent and did not know of the scheme.

Lula himself is scheduled to testify on Wednesday, and court officials have said they expect a ruling by July in the case.

The Petrobras probe has unearthed the largest corruption scheme known in Brazil.

Billions have been paid in bribes, mainly by construction companies, to win contracts with Petrobras and other state-run companies. Over 80 people have been convicted, and the Supreme Court last month approved the investigations of nearly one-third of President Michel Temer’s Cabinet, 12 governors and dozens of top federal lawmakers.