GRAND ISLAND, Neb. – A dangerous chemical reaction injured five workers and forced the evacuation of a JBS Swift beef processing plant.

The incident occurred around 10 p.m. April 14 when bleach was accidentally pumped into a lactic acid storage tank. The mixture of chemicals produced toxic gas. Five workers were treated for exposure and released the same day.

“JBS officials at the Grand Island plant responded swiftly to the accident, evacuating the approximately 30 maintenance workers who were on site, and calling the fire department as a precaution,” the company said in a statement. “Plant officials will review the incident and implement additional preventive measures as necessary.”

The plant was not operating at the time and production was not interrupted.

The ventilation system was used to clear out the gas, according to AP.