FRANKFURT (AFP) - German public prosecutors said Wednesday they have launched a preliminary criminal inquiry into the pollution cheating scandal that has engulfed auto giant Volkswagen.

"In connection with the allegations of emission gas manipulation in VW diesel engines, the public prosecutors of Brunswick are considering launching a probe against management employees at Volkswagen," the prosecutors said in a statement.

They explained they would first examine all possible information and evaluate a number of legal suits that have already been filed against the company by private individuals.

VW, the world's largest auto manufacturer by sales in the first half of this year, faces a growing tangle of legal threats after it admitted that as many as 11 million of its diesel cars worldwide are equipped with software capable of fooling official pollution tests.

According to the US authorities, VW has admitted that it equipped about 482,000 cars in the United States with sophisticated software that covertly turns off pollution controls when the car is being driven.

It turns them on only when it detects that the vehicle is undergoing an emissions test.

With the so-called "defeat device" deactivated, the car can spew pollutant gases into the air, including nitrogen oxide, in amounts as much as 40 times higher than emissions standards, said the US Environmental Protection Agency (EPA).

The EPA, which announced the allegations Friday along with California state authorities, is conducting an investigation that could lead to fines amounting to a maximum of more than US$18 billion (S$25.6 billion).

The US Department of Justice has also launched a criminal investigation led by its environment and natural resources division, a source told AFP, speaking on condition of anonymity.

The California Air Resources Board, too, is investigating Volkswagen's pollution violations.

New York Attorney General Eric Schneiderman said he had launched his own probe of Volkswagen and would work on it with prosecutors from other states across the United States.

Private law firms are lining up to take on the German company, with a class action suit already being filed by a Seattle law firm.