Marcelo Odebrecht, owner of Latin America's largest engineering and construction firm Odebrecht SA, was arrested at his Sao Paulo home in a pre-dawn raid Friday, police said.

Otavio Marques de Azevedo (pictured above), president of major Brazilian construction company Andrade Gutierrez, was also arrested in the sweep.

Prosecutors say at least $800 million (75.5 million euros) was paid in bribes by construction and engineering firms in exchange for inflated Petrobras contracts. The excess funds were then funneled into the coffers of executives, politicians and parties, including the ruling Workers' Party.

"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 a 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.

Petrobras, Brazil's largest company, estimates it lost more than $2 billion in the graft scheme dating back to at least 2004.

Marcelo Odebrecht was one of several executives rounded up on Friday

Arrests 'unnecessary'

Since an investigation was launched in March 2014, dozens of politicians and business directors have been accused of financial crimes including corruption and money laundering.

President Dilma Rousseff, who was chairwoman of the Petrobras board from 2003 until 2010, has denied knowledge of wrongdoing and urged a thorough investigation.

Odebrecht SA Friday issued a statement saying the arrests were "unnecessary" because it was cooperating with investigators.

"The firm and its executives...have always been available for the authorities to cooperate with the investigation," Odebrecht said.

Andrade Gutierrez insisted that it has "never had any ties to the events that are under investigation" and that the company "hopes to clear up any doubts before the courts as soon as possible."

nm/cmk (Reuters, AP, AFP, dpa)