German authorities arrested the CEO of Volkswagen's Audi division as part of a probe into manipulation of emissions controls on Monday.

Rupert Stadler was detained because investigators worried that he might seek to suppress evidence in connection with the investigation, Munich prosecutors said. His home was searched last week.

"The suspect has been seen by a judge, who has ordered him to be remanded in custody," the prosecutors' office said in a statement.

Authorities last week widened the emissions cheating probe into Volkswagen's luxury brand Audi to include Stadler among the suspects accused of fraud and false advertising.

A total of 20 people are under suspicion in the Audi probe, which focuses on cars sold in Europe that were believed to be equipped with software that turned emissions controls off during regular driving.

Volkswagen has pleaded guilty to criminal charges in the United States and nine managers, including former CEO Martin Winterkorn, were charged there. Two are serving prison terms; Winterkorn and the others remained in Germany and are unlikely to be extradited. Audi said in a statement last week that it was "cooperating with the authorities" in the probe.

The scandal first broke in 2015 when the Environmental Protection Agency accused VW of installing a so-called defeat device in products such as the Jetta TDI equipped with 2.0-liter diesels. The engine control software was programmed to reduce emissions to legal levels when the vehicle underwent testing. In normal use, however, pollution levels increased as much as 40-fold.

In 2017, a U.S. federal judge ordered Volkswagen to pay a $2.8 billion criminal penalty negotiated as part of a settlement with the U.S. Justice Department.

In total, VW has incurred more than $30 billion in costs over the scandal — a figure that includes the price of buying back almost 500,000 vehicles sold in the U.S.