Globo daily said the five include Paulo Roberto Costa, a jailed former Petrobras director who exposed the massive scope of the alleged payments to Brazilian politicians, dubbed "Operation Car Wash."
Globo said Costa has pledged in writing to return USD 27 million, most of which is parked in a Swiss bank account, the report said, citing sources close to the investigation.
O Estado de Sao Paulo reported yesterday that another former Petrobras director, Pedro Barusco, had agreed to pay back USD 100 million and cooperate with investigators.
Currency dealer Alberto Youssef, accused of money laundering in the case, has reportedly pledged to hand back some USD 19.2 million and two businessmen from construction firm Toyo Setal say they would hand back a similar sum.
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As much as four billion dollars were allegedly paid to members of the ruling Workers Party and other politicians, between 2004 and 2012 to buy influence with cash creamed off inflated Petrobras contracts.
Some of those arrested on suspicion of corruption and money-laundering include top executives from some of Brazil's biggest construction firms.
Brazil's President Dilma Rousseff says she had no knowledge of the kickback scheme, even though senior members of her ruling Workers Party have been linked to it.
Nobody has been convicted to date but dozens of arrests have been made and Costa is set to stand trial.