The latest inquiry involves more than 309,000 TrailBlazer SUVs from the 2006 and 2007 model years. The fires began in the power window switch or related electrical parts, the National Highway Traffic Safety Administration said Monday.
The agency opened the first probe last week into similar problems with the 2007 Toyota Camry sedan and RAV4 small crossover SUV. The TrailBlazer investigation began Thursday.
All three of the vehicles under investigation are popular. None has been recalled.
The TrailBlazer, although phased out in the U.S. in 2009, was among GM's top-sellers. The Camry was the best-selling car in the U.S. in 2007 and last year.
The agency has received 12 complaints of smoke or fires in TrailBlazers. No injuries have been reported, says the SUV's maker, General Motors Co. None of vehicles that caught fire was destroyed, although some door parts melted and seats were singed, the automaker says.
Several of the TrailBlazer fires happened while the SUVs were moving. Others occurred when the engines were off and the vehicles were unattended.
In one complaint filed with NHTSA, from Oct. 29, 2008, a woman reported that the alarm sounded while her 2006 TrailBlazer was parked in her driveway. When she looked outside, she saw the SUV in flames. Firefighters put out the blaze and told her it started in the driver's door.
"The fire burned the entire driver's side of the vehicle, a portion of the front passenger seat and the roof," she wrote.
GM believes the condition is restricted to the 2006 and 2007 model years. That is because of a parts change made for the 2006 model year that lasted through the end of the 2007 model year, says spokesman Alan Adler.
A NHTSA spokeswoman said the agency is in the process of finding out if GM and Toyota Motor Corp. got switches from the same parts maker, and if any other vehicles had them.
Neither GM nor Toyota would identify its parts supply company because the investigation is under way.
Three other GM vehicles built on the same undercarriages as the TrailBlazer have the same power window switches, but no fires have been reported in the Buick Ranier, GMC Envoy or Saab 9-7X, Adler said. The other vehicles have different door configurations than the TrailBlazer, he said.
Any TrailBlazer owner who smells burning plastic or whose power windows stop working should contact their dealer, he said.
The TrailBlazer helped to make truck-based SUVs popular in the U.S. during the early 2000s. The SUV was replaced by more the more efficient Chevrolet Traverse, which is built on a car frame. GM sold 309,423 TrailBlazers in 2006 and 2007.
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. Both GM and Toyota said they are cooperating with NHTSA in the investigation.
GM shares fell 17 cents to close at $25.33. Toyota shares rose 52 cents to close at $78.91.