Volkswagen U.S. CEO Michael Horn speaks at the 2015 Los Angeles Auto Show on Nov. 18, 2015. David McNew/Getty Images

The U.S. subsidiary of German auto giant Volkswagen AG announced company President and CEO Michael Horn was leaving effective immediately. VW said Horn, 54, was leaving “to pursue other opportunities.”

Volkswagen Group said Hinrich J. Woebcken will take over as Volkswagen Group of America’s interim CEO. He was recently appointed head of the North American region.

Horn, a German citizen and 25-year veteran of the world’s second-largest automaker, assumed the presidency of Volkswagen Group of America in January 2014, four months before scientists in West Virginia discovered emissions violations in the company’s small “clean diesel” engines.

“During his time in the U.S., Michael Horn built up a strong relationship with our national dealer body and showed exemplary leadership during difficult times for the brand,” Herbert Diess, CEO of the company’s Volkswagen division, said in a statement.

Last year, the company admitted to installing software that allowed nearly 600,000 Volkswagen and Audi cars in the U.S. to cheat lab emissions testing. About 11 million vehicles are affected worldwide, leading to civil charges and class-action lawsuits from angry customers.

Horn, who has been in charge of the company’s relations with its dealership network, has not been implicated in any wrongdoing, but other company higher-ups could face fraud charges in Germany or the U.S.

Meanwhile, California regulators said Tuesday it may allow Volkswagen diesel cars to remain partially fixed because full repairs may not be possible. California is home to about 80,000 of the affected vehicles.“We will have to decide what the best approach is to dealing with these vehicles, and one of the options potentially would be to accept something less than a full fix,” said Todd Sax, chief of the California Air Resources Board enforcement division.