GM battery lab explosion outside Detroit injures five (Update)

UPDATE: An explosion and fire this morning triggered by a lithium-ion battery injured five people at the General Motors Tech Center in Warren, Mich., just outside Detroit. GM says the incident required the evacuation of the Tech Center; the Detroit Free Press reports that one worker is in critical condition at an area hospital.Video from the scene shows windows blown out of the lab, part of the sprawling campus where GM engineers and designs future vehicles. Warren fire officials have said the blast was caused by a lithium-ion battery reaction, but GM has declined to specify a cause.

GM spokesman Greg Martin said fire and emergency crews were called to the site about 8:45 a.m., and that all employees have been accounted for. GM said the incident was "related to extreme testing on a prototype battery," not any model in production today.

The 33,000-sq. ft. lab at the Tech Center was the largest of its kind when GM opened it in 2009 to research future batteries for vehicles such as the Chevrolet Volt. All automakers who build electric vehicles use lithium-ion cells, typically designed to minimize fire risks even when damaged. But such batteries can still overheat when mistreated, as federal regulators found when they left a fully charged Volt sit for weeks following a crash test.

To test their batteries, automakers often put them through abusive and destructive exams, from hundreds of quick charge/discharge cycles to even shooting them to measure resistance to puncture damage.