DETROIT >> For the second time in a week, federal safety regulators have started investigating reports of fires in the driver’s side doors of vehicles.

This time, the probe involves more than 309,000 Chevrolet TrailBlazer sport utility vehicles from the 2006 and 2007 model years. Documents posted on the National Highway Traffic Safety Administration website on Monday say that the fires began in the driver’s side power window switch or related electrical parts.

The agency has received 12 complaints, including 10 involving fires. General Motors Co. said that none of the fires have destroyed the SUVs, but some had melted door parts and singed seats. No injuries have been reported, company spokesman Alan Adler said.

NHTSA began investigating the TrailBlazer on Thursday, just three days after it opened a probe into similar problems with the 2007 Toyota Camry and RAV4.

It was unclear if GM and Toyota Motor Corp. got switches from the same parts maker. Adler said he didn’t know where the parts came from, and a message was left for Toyota’s safety spokesman in Torrance, Calif.

In the TrailBlazer cases, several of the fires happened while the SUVs were moving, while others happened when the engines were off and the vehicles were unattended.

GM believes the condition is restricted to the 2006 and 2007 model years due to a parts change that was made for the 2006 model year that lasted through the end of the 2007 model year, Adler said.

Six Camry and RAV4 fires were reported to NHTSA, but there were no reports of injuries. Most of the fires were minor with damage limited to the doors, but a Camry was destroyed in one case, according to complaints filed with NHTSA.

The Toyota investigation involves more than 830,000 vehicles. The Camry was the top-selling car in the U.S. in 2007.

Both GM and Toyota said they are cooperating with NHTSA in the investigation.

GM shares rose 26 cents to $25.76 in morning trading Monday while Toyota’s U.S. shares rose 65 cents to $79.04.