The head of the National Highway Traffic Safety Administration is telling Congress the agency "pulled no punches" in its investigation into Chevy Volt batteries that caught fire last year.

Republicans on the House Committee on Oversight and Government
Reform repeatedly raised questions about whether the government's
partial ownership in General Motors created a conflict of interest as it investigated the electric car. Republicans also challenged why the agency took several months to inform the public about last June's fire.

The committee chairman, California Republican Darrell Issa, told agency head David Strickland at the combative hearing Wednesday: "I hear you, I don't believe you."

The government ended its investigation last week, concluding that the Volt and other electric cars don't pose a greater fire risk than gasoline-powered cars.