The General Motors Technical Center had an explosion Wednesday morning while conducting a test on lithium-ion batteries for electric cars.

The company who produces electronic car Chevrolet Volt said the explosion happened around 8:45 a.m. EDT in its laboratory in Warren, Mich., starting a fire in the facility. The city’s Fire Chief David Frederick told Bloomberg that at least two seriously injured people were taken to a hospital. At least four were treated at the scene while 80 workers were forced to evacuate.

“Chemical gases from the battery cells were released and ignited in the enclosed chamber,” said GM in a statement. “The battery itself was intact.”

The safety issue of an electric car, especially the Chevy Volt, has been a serious topic recently. After the federal investigation Volt’s battery last November, the sales of the model took a major blow.

GM however said in a statement that the explored battery was not intended for the Volt plug-in electric car.

“The incident was related to extreme testing on a prototype battery,” said GM in the statement.

The damage of the fire was minimized as firefighters arrived five minutes after the incidents. The estimate of the damage is not available at the moment.

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