``We have conferred with our certified explosives experts and have no reason to believe that the explosion was deliberately caused and was indeed an accident,' said Earl Woodham, a spokesman for the Bureau of Alcohol, Tobacco and Firearms. ``Therefore, because we found no criminal cause or intent, the criminal investigation is now closed.'The blast at Melrose South Pyrotechnics killed James Brett Ringer, 24, of Rock Hill, and injured Kenny Vinson and Heather Arnette.

Woodham would not say what caused the explosion because that information could compromise an investigation by state Occupational Safety and Health Administration officials.