Federal government officials believe the Chevy Volt poses no greater risk for post-crash fires than conventional gasoline-powered cars.

That's the conclusion of a two-month investigation that examined potential hazards involving General Motors' flagship electric vehicle and its battery pack.

In a statement released Friday, the National Highway Traffic Safety Administration concluded "no discernible defect trend exists" and that battery-pack modifications recently announced by GM would reduce potential for future problems resulting from side-impact accidents.

NHTSA opened its investigation in late November after tests last May showed damage to the car's lithium-ion battery could result in post-crash fires, sometimes even weeks after accidents. While no real-world examples of the sequence were ever recorded, the government agency said it investigated because of the "innovative nature of this emerging technology."

In response to the investigation, GM announced in December that it had reinforced the structure around the Volt's battery pack to spread impact forces in severe side-impact collisions and added sensors to monitor coolant levels.

"We want to provide that peace of mind for our customers, that even in a severe side crash, their vehicles will not have an issue," said Mary Barra, GM's senior vice president for global product development.

Neither NHTSA nor the automaker mandated a recall of the approximate 8,000 Volts on roads today, but Volt owners can have modifications made on their cars through a voluntary program. The alterations add approximately 2 to 3 pounds to vehicle weight, and dealers should have parts in stock in February.

Although NHTSA may be finished with its Volt investigation, its statement indicates that close scrutiny of the emerging electric vehicle fleet may be ongoing.

"NHTSA continues to believe that electric vehicles show great promise as a safe and fuel-efficient option for American drivers," officials said in the written statement. "Recognizing these considerations, NHTSA has developed interim guidance -- with the assistance of the National Fire Protection Association, the Department of Energy and others -- to increase awareness and identify appropriate safety measures for these groups."

Sales of the Volt seemed unblemished by the investigation. GM sold 7,671 Volts in 2011, below the company's stated goal of 10,000. But in December, the company sold 1,529 units, the model's best sales month ever.

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