The National Highway Traffic Safety Administration (NHTSA) has intensified a investigation of 21 models of General Motors trucks and SUVS manufactured between 2006 and 2008 because of the possibility of an engine compartment fire.

More than 2,700,000 GM trucks and SUVs are the subject of the the investigation because of the possibility that a fire might erupt inside the engine compartment, even when the ignition is turned off.

The Office of Defects Investigation (ODI) at the federal safety agency reported that investigators are now aware of "41 non-crash engine compartment fires" in the GM trucks and SUVs including 8 fires that may have caused significant property damage.

The GM vehicles under investigation are:

• 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
•the Hummer H2 from the 2006 to 2008 model years.

"GM provided ODI with 41 allegations of non-crash engine compartment fires including 16 allegations of fires origination with the ignition in the off position," according to the NHTSA Web site.

Investigators are examining the electrical system, engine and engine cooling system; battery cables; under-hood wiring, fuses and circuit breakers.

NHTSA investigator are now call the probe an "engineering analysis" which could eventually lead to a recall of the General Motors trucks and SUVs.