Brazilian police said they arrested the presidents of two of the country's largest construction companies on Friday for their alleged involvement in the massive corruption scheme at the country's state-run oil company, Petrobras.

Federal Police inspector Igor Romario de Paulo said at a news conference that Marcelo Odebrecht and Otavio Marques de Azevedo were taken into custody and face charges of cartel formation, money laundering and diversion of public funds. They are the chief executives of Odebrecht and Andrade Gutierrez respectively.

Another eight executives from the two companies were also arrested. They will be taken to the southern city of Curitiba, where the investigation is based.

"We have money-laundering professionals in Brazil and we have no doubt that Odebrecht and Andrade Gutierrez headed the cartel scheme inside Petrobras," federal prosecutor Carlos Fernando dos Santos Lima said at the news conference. "I do not see how the companies can claim innocence given how much evidence we have."

He said the two men "had a sophisticated system" for making the alleged bribe payments, using foreign bank accounts in Switzerland, Monaco and Panama.

Prosecutors have said the scheme involved at least $800 million in bribes and other illegal funds. Some of that money was allegedly funneled back to the ruling Workers' Party and its allies' campaign coffers. It also allegedly included the payment of bribes to Petrobras executives in return for inflated contracts.

Petrobras is Brazil's biggest company and is in charge of tapping big offshore oil fields and creating wealth that leaders hope will propel the country to developed world status.

Odebrecht said in a statement sent by email that police searched the company's offices in Sao Paulo and Rio de Janeiro and that it considered the police operation unnecessary because Odebrecht was cooperating with the investigation.

In a similar statement, Andrade Gutierrez also said it was cooperating with authorities and denied any wrongdoing.