FRANKFURT -- German prosecutors are saying their probe of former Volkswagen CEO Martin Winterkorn is ongoing and won't be affected by the charges brought against him in the United States.

"We have taken account of the U.S. indictment, but it will not change our investigatory approach," said Klaus Ziehe, spokesman for the prosecutors in the town of Braunschweig.

The German prosecutors are investigating Winterkorn and 48 others in connection with the emissions scandal. U.S. authorities charged Winterkorn on Thursday with fraud and conspiracy in connect with use of illegal software used to cheat on U.S. diesel emissions tests.

Winterkorn's U.S. attorney, Steven Molo, said that "we are reviewing the allegations and will take appropriate actions."

Winterkorn resigned days after the U.S. Environmental Protection Agency accused Volkswagen of evading emissions standards. Cars were equipped with software that turned on emissions controls when the cars were on test stands, and reduced the controls during normal driving. Winterkorn said at the time he was not aware of any wrongdoing on his part.

The company pleaded guilty to criminal charges and has paid more than $20 billion in fines and civil settlements. Two lower-ranking Volkswagen executives have been sentenced to prison in the United States, while five others have been charged but not been apprehended.

It's unclear whether Winterkorn or any of the other defendants will ever face proceedings in the United States. Germany's constitution in general forbids extradition of its citizens except to another EU member state or to an international court. If Winterkorn travels outside Germany he could face arrest and possible extradition to the United States.