Fiat Chrysler (FCAU) - Get Report shares fell in New York trading Tuesday following a report that the U.S. Department of Justice is preparing to file a civil suit against the carmaker for violating the Clean Air Act as early as tomorrow.

Fiat shares were marked more than 0.9% lower at $10.66 by 11:30  Eastern, extending a month-to-date decline of around 6.8%, after Reuters reported, citing sources, that the DoJ would file the suit Wednesday.

Reports that the DoJ is preparing a civil suit against the carmaker following a probe that was opened in January related to excess diesel emissions surfaced earlier this month. The group has also been accused by the U.S. Environmental Protection Agency of failing to disclose engine management software in its vehicles, including Jeep Cherokees and Dodge Ram trucks, which could result in an emissions output that was too high. Investigators also said at the time that they would look at whether software in Fiat-Chrysler vehicles constitutes a defeat device.

Speculation of imminent action from the DoJ comes closely on the heels of a European Commission declaration that it is taking action against the Italian government for what, it said, was a failure to enforce Brussels' emissions-related laws.

British authorities also said, back in January, that they have requested information relating to the probe from their American counterparts.

The emissions scandal also impacted shares of Germany's Daimler AG (DDAIY)  , which fell in Frankfurt Tuesday after the luxury carmarker said German authorities searched the company's offices in Stuttgart as part of an ongoing probe into emissions manipulation.

Daimler shares were marked more than 0.85% lower at €67 each after trading in positive territory for much of the session. The benchmark DAX performance index, by contrast, was quoted 0.31% higher while the Stoxx Europe 600 Automobiles and parts index was seen 0.63% lower on the session.

"In connection with its preliminary investigations of known and unknown employees of Daimler AG due to suspicion of fraud and criminal advertising relating to the possible manipulation of exhaust-gas after treatment in passenger cars with diesel engines, the Stuttgart public prosecutor's office is about to search premises of Daimler AG at several locations in Germany," Daimler said in a statment. "The company is fully cooperating with the authorities."