FRANKFURT — Mitsubishi Motors is under investigation for possibly selling diesel vehicles in Germany that had been programmed to cheat on emissions tests, Frankfurt prosecutors said Tuesday as the police raided offices of the Japanese carmaker.

The investigation is another setback for the Renault-Nissan-Mitsubishi alliance, which has been under severe strain since the arrest of Carlos Ghosn, its former chairman, more than a year ago in Japan.

Another diesel emissions scandal could also weigh on the entire auto industry. Accusations of emissions cheating against Volkswagen, Fiat Chrysler, Daimler and others have hurt the reputations of the traditional carmakers when they are under fierce pressure from Tesla and its emission-free electric cars.

Investigators raided 10 offices in and around Frankfurt, near Munich and in other locations around Germany on Tuesday, the prosecutors said. The searches included two suppliers, which the authorities did not identify.