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MIAMI (CBSMiami) – While getting grilled on Capitol Hill on Thursday, the head of Volkswagen’s American group said the company is sorry for cheating on government emissions tests.

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“I would like to offer a sincere apology for Volkswagen’s use of a software program that served to defeat the regular emissions testing regime,” said Michael Horn, CEO for Volkswagen Group of America.

Up to 11 million Volkswagen diesel cars had sophisticated software installed which would reduce toxic emissions during testing. The software would then shut off allowing emission levels to climb 10 to 40 times above EPA levels.

“The American people, the EPA and their counterparts around the world have been defrauded by Volkswagen. The company’s word isn’t worth a dime,” said Rep. Jan Schakowsky (D) Illinois.

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Volkswagen first became aware of a problem with emissions standards after a West Virginia University study was published in the spring of 2014 but the company’s American CEO claimed he didn’t know the full extent of the problem.

Rep. Timothy Murphy asked, “At that time, were you aware, or informed, that these vehicles contained defeat devices?”

“No,” said Horn.

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U.S. regulators aren’t the only ones going after Volkswagen.  German prosecutors raided the company’s German headquarters on Thursday to secure documents and data storage devices.