More than 400 pounds of ammonia and a small amount of ammonium chloride escaped from the Olin Corp. complex yesterday when a transformer caught fire and knocked out power to part of the facility.

Officials said that no injuries were reported and that the leak was under control about an hour after it was discovered.

The leak was the second accidental release of chemicals in South Charleston in less than a week and the sixth chemical leak in "Chemical Valley" within a month. About 10,000 pounds of diluted hydrochloric acid leaked from Union Carbide's South Charleston unit Monday night. Company officials said that leak was the result of a "gasket failure." No injuries were reported.

On Aug. 11, a leak of pesticide chemicals at Union Carbide's plant at Institute made 135 people ill in the first of a series of chemical leaks from various plants and tanker trucks in the Kanawha Valley.

Yesterday's release of nontoxic chemicals used to produce dry bleach "was a direct result of the power failure" caused by the transformer fire, Ron Engle, chief chemist for the state Air Pollution Control Commission, said.

The leak prompted South Charleston police to close a section of U.S. 60 through the city for about 20 minutes when the ammonia vapor spread from the plant. The ammonia is considered a mild irritant, according to Olin Corp. spokesman Alex Houston.