The National Highway Traffic Safety Administration (NHTSA) has intensified an investigation of 21 GM truck and SUV models manufactured between 2006 and 2008 because of the possibility of an engine compartment fire. More than 2.7 million vehicles are now subject to the investigation, which originally only concerned 400,000 2007 Chevrolet Tahoes and GMC Yukons.

The vehicles are being examined for the possibility of a fire erupting in the engine compartment, including when the vehicles are turned off. The investigation was expanded after the agency received 41 non-crash engine fires, including 16 when the ignition was in the off position.

No reason has been found yet but areas being looked at include the vehicles' electrical systems, engine cooling systems, battery cables, under-hood wiring, fuses, and circuit breakers. The investigation is currently in the ‘engineering analysis’ phase but could eventually lead to a recall of all 2.7 million models if a problem is found. The affected models are listed below.

• Cadillac Escalade ESV and EXT from the 2007 and 2008 model years,

• Chevrolet Avalanche 1500 from the 2007 and 2008 model years,

• 2007 Chevrolet Avalanche 2500,

• 2007 Chevrolet Silverado,

• Chevrolet Silverado 1500, 2500 and 3500 from the 2007 and 2008 model years,

• Chevrolet Surburban 1500 and 2500 from the 2007 and 2008 model years,

• Chevrolet Tahoe from the 2007 and 2008 models year,

• 2008 GMC Sierra,

• GMC Sierra 1500, 2500 and 3500 from the 2007 and 2008 model years,

• 2007 GMC Sierra Classic,

• 2007 GMC Silverado, GMC Yukon from the 2007 and 2008 model years,

• GMC Yukon XL 1500, XL 2500 from the 2007 and 2008 model years,

• Hummer H2 from the 2006 to 2007 model years,

• 2008 Hummer H2 Utility, and

• Hummer H2 from the 2006 to 2008 model years.