MINNEAPOLIS (WCCO) — Volkswagen stock closed down 20 percent Tuesday for the second straight day as the scandal at Volkswagen continues to grow.

The German car manufacturer admitted Tuesday that software designed to cheat emissions tests was installed in 11 million cars worldwide.

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The scandal prompted an apology from Volkswagen USA CEO Michael Horn.

“Our company was dishonest with the EPA,” Horn said. “And in my German words, we have totally screwed up.”

The affected models are all diesels and include the 2009 to 2015 Volkswagen Jetta, 2009-15 Beetle, 2009-15 Golf, 2014-15 Passat and 2009-15 Audi A3.

Local Volkswagen dealers WCCO contacted declined to comment. Mark Carden, the general sales manager at Luther Westside Volkswagen, gave this statement: “We are going to do all we can to make everyone happy. Right now we don’t have enough information.”

Professor Fred Zimmerman has written extensively on the auto industry.

“This is a huge deal. This is going to be a problem not only for Volkswagen, but it’s going to cause a lot of scrutiny for the other manufacturers,” Zimmerman said.

The U.S. Environmental Protection Agency says affected owners should get notices in coming weeks and months on where they can get their cars fixed for free. Experts warn that the fix will affect performance.

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“They’ll be less fuel efficient and they won’t have as much pep,” Zimmerman said.

Volkswagen has been leading a push towards wider consumer acceptance of diesel models which are more fuel efficient but emit more pollutants. And that is why intentionally cheating on emissions tests is not sitting well with local consumers like Volkswagen owner Sue Dahl, even though her Beetle is not one of the models affected

“I think that’s very concerning,” Dahl said. “It’s also concerning I think about other car makers. Are they doing the same? How do we know?”

Sen. Al Franken called Volkswagen’s conduct “terrible” in a statement released Tuesday.

“The company must be held accountable for its actions,” Franken said.

Sen. Amy Klobuchar commented Tuesday on the scandal.

“Volkswagen’s deliberate deception of consumers and regulators is inexcusable for a company that many Americans have trusted for decades,” Klobuchar said. “With 11 million vehicles affected around the world and nearly half a million here in the United States, this behavior merits a full and thorough investigation from the U.S. Department of Justice.”

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Sources tell CBS News the Department of Justice has opened a criminal investigation into Volkswagen’s actions.

Esme Murphy