State environmental officials say four workers at a metal cutting plant in Old Saybrook have been taken to the hospital following a fire that exposed them to smoke that could be toxic.

The fire took place Thursday evening at Sound Manufacturing, which uses a laser in its metal cutting operation. Officials say equipment there caught fire, raising concern that a substance coating the equipment's lens could have released toxic and flammable vapors after being exposed to heat.

The employees are being evaluated at Middlesex Medical Center in Essex. Officials say they appear to have symptoms of respiratory irritation.