Workers at a plant specializing in the surface treatment of metals were exposed to cyanide Thursday in Merignac, France, with five people subsequently hospitalized.

Forty emergency responders were called to the scene to identify the source of the leak and pump the spilled cyanide into a retention tank, a government website states.

Responders immediately confined the entire workforce of 35 to the factory’s main building. A security perimeter was set up firefighters and police.

At least eight workers show symptoms of exposure to cyanide gas such as headache and vomiting. Five were transported to hospital for treatment. The remaining workers confined to the factory were later released.

The factory was last subject to an official inspection in July 2019.