Louisville, Ky. ? An explosion ripped through a food additive plant Friday, killing a worker and spewing a cloud of ammonia over parts of Louisville.

Residents near the D.D. Williamson & Co. plant were asked to stay inside their homes and some were evacuated after the explosion at 2 a.m. shook windows more than three miles away.

The blast ruptured a tank holding 40,000 pounds of ammonia. Firefighters tried to control the leak, but the tank was empty six hours later.

Five workers were inside the plant at the time of the explosion. Four escaped uninjured, but the fifth — Louis C. Perry, 44, of Louisville — was killed.

Perry had noticed the leaking tank and was walking toward the area at the time of the blast, Fire Capt. Ronel Brown said. Jefferson County Deputy Coroner Eddie Robinson said he died of multiple blunt force trauma from the explosion.

The plant makes caramel coloring for food products and drinks. The ammonia was used as a refrigerant, said R.N. Bartlett, spokesman for Jefferson County Emergency Management.

Ammonia inhaled at high doses can be fatal, but the levels released after the explosion were not dangerous, he said. The warnings to area residents were lifted about six hours after the explosion.

Safety inspectors have visited the plant six times since 1985, resulting in four “serious” citations.