German prosecutors investigating whether carmaker Daimler manipulated emission tests on its diesel cars are looking at whether auto components supplier Bosch was involved in the alleged fraud, it was confirmed last week.

“There is an investigation into aiding and abetting fraud,” a spokesman for the Stuttgart prosecutor said following a media report published last Thursday.

The spokesman added that the Bosch investigation started a couple of weeks ago and was tied to the continuing probe of Daimler, the owner of the Mercedes-Benz brand.

Bosch is a provider of engine management software to Daimler and prosecutors are investigating whether the carmaker made use of illegal software to cheat emissions tests.

The latest investigation of Bosch in connection with Daimler comes in addition to a separate inquiry in which Stuttgart prosecutors are looking at what role Bosch may have had in helping engineers at Volkswagen manipulate diesel emissions.

The new probe targets “unknown individuals”, the spokesman for the public prosecutor’s office said.

A spokesman for Bosch said: “As a matter of policy, and due to the sensitive legal nature of these matters, Bosch will not comment further concerning matters under investigation and in litigation.”

This week prosecutors searched Daimler’s offices as part of the investigation into diesel emissions and said they were in touch with the US authorities. Earlier this month a US federal judge gave final approval for Bosch to pay almost €300 million to US owners of VW diesel cars for its role in developing the engines and as part of a broader settlement to buy back the polluting vehicles. Bosch admitted no wrongdoing in the settlement.