Auto supplier Bosch has rejected lawsuit allegations that it participated in Volkswagen’s decades-long fraud to cover up diesel-engine emissions, calling the claims “wild and unfounded.”

Robert Bosch GmbH responded to lawsuits against Volkswagen AG on behalf of U.S. owners of VW diesel cars Monday in a U.S. District Court filing in San Francisco. Attorneys in these suits have stated that German supplier Bosch was a “knowing and active participant in the scheme,” according to coverage in Reuters.

Bosch has supplied an engine control unit to VW and several other automakers. The company supplied software and components to VW, but has said that how the software is used for regulating exhaust emissions is up to the automaker to determine.

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Bosch said that a review of the plaintiffs’ documents “indicates that the plaintiffs have made wild and unfounded allegations.” In some cases, these allegations are based on speculation, the Bosch filing said.

The allegations involving Bosch have been under seal because the documents have been designated as confidential by VW. Bosch said the plaintiffs’ complaint cites 38 Bosch employees.

Bosch’s potential role in the diesel-emissions scandal has gone back to late last year. In December, German prosecutors said that they were investigating whether the company was involved in the manipulation of emissions tests by VW.