BERLIN (REUTERS) - Volkswagen managers are worried about travelling to the United States, a German newspaper reported on Saturday, saying US investigators have confiscated the passport of an employee who is there on a visit.

Citing company sources, the Suddeutsche Zeitung said Volkswagen believes the investigators want to prevent the manager from evading questioning or criminal prosecution linked to the diesel emissions scandal.

A spokesman for Volkswagen said: "Volkswagen employees are still travelling to the United States. Everything else is speculation."

Volkswagen is under investigation in the United States and could face penalties of up to US$18 billion (S$25 billion) after admitting it deliberately rigged emissions tests of diesel-powered vehicles.

Mary Nichols, head of the California Air Resources Board, which is investigating Volkswagen, has criticised the carmaker's handling of the scandal.

Citing a person with knowledge of the matter, the paper said it was now unlikely that new Volkswagen chief executive Matthias Mueller would travel to the United States in the second half of November as planned.

"We need legal security here before he can fly to the United States," the paper quoted a person from group management as saying.

There is no official plan for Mueller to travel to the United States, and Volkswagen declined to comment when asked whether such a trip was likely.