U.S. prosecutors are investigating whether Germany’s Robert Bosch GmbH, which provided software to Volkswagen AG, conspired with the automaker to engineer diesel cars that would cheat U.S. emissions testing, according to two people familiar with the matter.

Among the questions the Justice Department is asking in the criminal probe, one of them said, is whether automakers in addition to VW used Bosch software to skirt environmental standards. Bosch, which is also under U.S. civil probe and German inquiry, is cooperating in investigations and can’t comment on them, said spokesman Rene Ziegler.

The line of inquiry broadens what is already the costliest scandal in U.S. automaking history. Wolfsburg-based VW faces an industry-record $16.5 billion, and counting, in criminal and civil litigation fines after admitting last year that its diesel cars were outfitted with a “defeat device” that lowered emissions to legal levels only when it detected the vehicle was being tested.

More than a half dozen big manufacturers sell diesel-powered vehicles in the U.S. The people familiar with the matter declined to say whether specific makers are under scrutiny.

Second Supplier

A second supplier may also be part of the widening probe: When prosecutors in Detroit outlined their case last week against a VW engineer who pleaded guilty to conspiracy in the matter, they said he had help from a Berlin-based company that is 50 percent owned by Volkswagen, described as “Company A” in a court filing. That company, according to a another person familiar with the matter, is IAV GmbH, which supplies VW and other automakers.

IAV employees were part of a group working with Bosch and VW to develop emissions functions, according to U.S. court filings in a separate case.

IAV didn’t respond to requests for comment. Volkswagen said it is continuing to cooperate with the Justice Department. Peter Carr, a Justice Department spokesman, declined to comment.

In Germany, prosecutors have said they are investigating whether Bosch employees helped VW rig software to cheat on emissions tests. In the U.S., Bosch is defending itself against a civil suit by drivers who allege that it not only conspired with VW to develop defeat devices, but also asked for legal protection from VW if the devices were used on American roadways.

Bosch, in filings in San Francisco federal court, has called the suit “wild and unfounded.”

People familiar with the industry have said it’s common for carmakers to buy software from a company such as Bosch and adapt it to their own vehicles.

Diesel Universe

There’s a limited universe of diesel-engine vehicles sold in the U.S., including cars made by VW, Daimler AG and BMW AG and light trucks by General Motors Co., Ford Motor Co. and Fiat Chrysler NV Automobiles.

Bosch provides components for several of these, including GM’s GMC Sierra, Ford’s F-250, Fiat Chrysler’s Jeep Grand Cherokee and models by Daimler’s Mercedes-Benz.

Informed in general about a government look into whether automakers beyond Volkswagen may have used defeat devices, spokespeople for Daimler, Fiat Chrysler, BMW, GM and Ford declined to comment.

IAV, the parts-maker that is half-owned by Volkswagen, provides engineering and expertise to automakers mainly for new-car development, including software, electronics and technology support. Volkswagen is that company’s largest customer, according to documents unsealed last week in Detroit federal court, with other clients including Bosch, BMW, Chrysler, Ford, GM and Daimler.

Special Access

Under an agreement signed by VW and Bosch in 2006, IAV employees were among 35 individuals who were granted special access to documentation on “expanded software” created for certain emissions functions, according to a filing in a civil lawsuit. The agreement, which the plaintiffs say they received from VW during discovery in the case, shows the extent to which Bosch sought control over any modifications to its software, they allege in the filing. Bosch has yet to respond in court to the allegations.

Beyond VW, other automakers face emissions-cheating lawsuits in the U.S. or accusations overseas of poor emissions performance.

Daimler said in April that it was asked by the Justice Department to investigate the certification process of its cars and is the subject of a lawsuit by car owners alleging some of its diesel cars violated emissions standards. Daimler, which said it was fully cooperating with U.S. authorities, has called the class-actions lawsuit “baseless.”

Daimler’s Mercedes-Benz has no 2017 diesel models listed among the more than 50 entries on the EPA’s fueleconomy.gov website. For 2016, the 70-plus models included the diesel-powered GL350 Bluetec SUV and E250 Bluetec sedan. The brand hasn’t announced a date for any diesel models to go on sale.

Earlier this month, the German Transport Ministry asked the European Union to investigate allegations that three Fiat Chrysler vehicles sold in Europe had defeat devices. Italy and Fiat have denied the accusations, with the Italian Transport Ministry sayings its own tests showed no unauthorized devices on the vehicles.

Other diesel vehicles in the U.S. include Nissan Motor Co.’s Titan XD pickup and Tata Motors Ltd.’s Land Rover Range Rover Sport Td6, which went on sale after the VW scandal erupted a year ago. Tata’s Jaguar has diesel versions of its 2017 F-Pace crossover and XE and XF sedans approved by the EPA and just starting to reach dealerships.