General Motors is insisting a fire at its Michigan alternative energy test chamber yesterday (11 April) is not linked to the Chevrolet Volt or any other vehicle.

In what the US manufacturer is describing as "an incident" at its energy centre in Warren, extreme testing of an experimental battery caused chemical gasses to be released and ignited.

Employees were evacuated from the facility, with five people extracted by medical personnel. One person has been admitted to an area hospital for treatment, but the seriousness of their condition is as yet unknown.

"Chemical gases from the battery cells were released and ignited in the enclosed chamber," said a GM statement sent to just-auto from its German headquarters.

"The battery itself was intact. The battery tested and the incident have no connection with the Chevrolet Volt or any other GM production vehicle. Employee safety is a priority at GM."

Last November, GM suffered two vehicle fires after batteries were punctured in crash tests.

Federal safety regulators closed their investigation of the fires after GM announced plans to strengthen the battery pack casing and install sensors to detect leaking battery fluid.

The City of Warren Fire Department in Michigan was not immediately available for comment.