A new study points to one company as the common link between multiple automaker’s diesel emissions troubles.

Robert Bosch Gmbh created the software that Volkswagen used to evade diesel emissions standards for years, while the same company also wrote the code for the alleged defeat device found in Fiat Chrysler Automobiles 3.0-liter diesels.

In the case of Volkswagen, the software used was able to detect when a vehicle was being tested for emissions and allow the vehicle to clean up its tailpipe to fool the test. Then, when back on the road, the cars were emitting up to 40 times the legal limit of pollutants.

“We find strong evidence that both defeat devices were created by Bosch and then enabled by Volkswagen and Fiat for their respective vehicles,” says the year-long study, undertaken by researchers at the University of California, San Diego and Ruhr-Universitat Bochum in Germany.

While Volkswagen has admitted to using defeat devices, FCA still claims it does not use a defeat device and that the brand will defend itself vigorously from these allegations. The Department of Justice recently announced a lawsuit against FCA over the alleged defeat device.

The authors of the study did admit that the documents they used that described Bosch’s technology did not come directly from the company, so they could not confirm their authenticity. The documents came from a VW portal meant for mechanics to access, but not directly from Bosch.

In a statement, Bosch declined to comment citing the “sensitive legal nature of these matters.”

The U.S. Justice Department (DOJ) is currently widening its criminal investigation into whether Bosch conspired with Volkswagen to specifically cheat on U.S. emissions tests.

While Bosch hasn’t been directly tied to any of this yet, the company has been named as a co-defendant in a number of class action lawsuits over diesel emissions from owners of VW, FCA, Mercedes-Benz and General Motors vehicles.

This article first appeared on AutoGuide