The government has upgraded an investigation into the Volkswagen Passat after receiving dozens of reports of engine fires.

The National Highway Traffic Safety Administration said in a posting on its Web site Tuesday that there had been 78 reports of engine fires and two injuries. The German automaker has received 14,850 warranty claims over the engine fires, the government said.

The investigation, which began in May, is focused on about 345,000 Passat sedans from the 2000-2003 model year. NHTSA said many of the complaints attribute the fires to a failure of the ignition coil.

Volkswagen has provided the government with information on the vehicle's three different engines and ignition systems. The investigation was upgraded to allow additional analysis.

VW spokesman Keith Price said the automaker was conducting its own investigation along with NHTSA.