By William Boston 

BERLIN -- The chief executive of Volkswagen AG's luxury unit Audi was arrested and imprisoned without bail after prosecutors said they were worried he might try to hinder a probe into whether he played a role in the German car maker's diesel emissions-cheating scandal.

The arrest of the executive, Rupert Stadler, came a week after Munich prosecutors searched his private residence and added him to a list of about 20 suspects in a broad fraud investigation stemming from the scandal.

Volkswagen admitted in 2015 to rigging nearly 11 million diesel-powered vehicles, including Audi models, with software that allowed them to cheat on emissions tests. The following year, the Audi unit was part of a broader settlement, in which Volkswagen pleaded guilty to defrauding the U.S. government. Volkswagen has incurred around $25 billion in penalties, fines, and compensation for customers stemming from the admission.

The scandal has also claimed a growing roster of Volkswagen executives. The U.S. has indicted eight, including former Chief Executive Martin Winterkorn, on charges of conspiracy to defraud the U.S. and to commit wire fraud, and to violate the Clean Air Act. Two are serving time in federal prison. Mr. Winterkorn, who has denied knowledge of the cheating, and the others remain in Germany, which has a law prohibiting the government from extraditing its citizens.

Meanwhile, various German probes into the cheating have been progressing more slowly. Mr. Stadler is the third person to be arrested by German authorities so far in connection with the diesel scandal.

A Munich prosecutor said Mr. Stadler was arrested at his home early Monday. A prosecutor in that office said investigators found evidence during the raid of Mr. Stadler's home last week that suggested he may try to disrupt the investigation.

"There was evidence that people and other suspects would be influenced. That's why we immediately issued an arrest warrant," state's attorney Stephan Necknig said. He didn't provide further details.

Mr. Stadler hasn't been charged with any wrongdoing. In Germany, it is common practice for prominent individuals suspected of a crime to be named by prosecutors in public. Being named a suspect doesn't mean the person will ultimately be charged. Mr. Stadler's attorney couldn't immediately be reached for comment.

A Volkswagen spokesman declined to comment, citing the ongoing investigation. Audi declined to comment on the allegations, saying only that "the presumption of innocence also applies to Mr. Stadler."

Last week, the Munich prosecutor's office added Mr. Stadler as a suspect to an investigation into fraud and illegal advertising in connection with the sale of more than 200,000 Audi vehicles in the U.S. and Europe that included illegal software that allowed the vehicles to cheat on emissions tests. Mr. Stadler hasn't commented. Audi declined to comment at the time, except to say it was cooperating in the probe.

In July last year, Munich prosecutors ordered the arrest of Zaccheo Giovanni Pamio, the former head of thermodynamics at Audi's engine development division. He has been released on bail, and it is unclear if he was charged with any offense. Mr. Pamio has been indicted in the U.S., which is seeking his extradition. Mr. Pamio's attorney couldn't immediately be reached for comment.

In September, Wolfgang Hatz, Volkswagen's former engine chief, was charged with fraud and illegal advertising resulting from the sale of Audi diesel vehicles. He has been held in custody pending trial. Mr. Hatz's attorney declined to comment.

--Ulrike Dauer and Markus Klausen contributed to this article.

Write to William Boston at william.boston@wsj.com

(END) Dow Jones Newswires

June 18, 2018 14:25 ET (18:25 GMT)