SAVANNAH - Dust collected in a piece of safety equipment caused a small explosion at a sugar refinery weeks before sugar dust beneath the plant's silos ignited to cause the deadly blast that killed nine workers, a federal investigator said Sunday.
Stephen Selk, investigations manager for the U.S. Chemical Safety Board, had few details about the previous explosion at the Imperial Sugar refinery in nearby Port Wentworth. He could not say whether the earlier blast contributed to the massive explosion Feb. 7.
'It is far too early to reach conclusions about the relationship between that event and this one,' Selk said.
Selk said no one was injured in the earlier explosion. He did not know the exact date, but said it happened 'weeks ago.'
The Chemical Safety Board investigates industrial accidents for the federal government and makes safety recommendations to industry and trade groups as well as federal regulators.
It has just begun looking into the refinery blast after criminal investigators determined Friday the explosion was accidental - caused by clouds of tiny sugar dust particles that, when airborne in confined spaces, can ignite like gunpowder.
Selk said the refinery was equipped with a network of fans and ducts designed to prevent dust explosions by sucking particles out of the plant and transferring them to dust collectors on the roof.
Ironically, it was one of those rooftop dust bins that exploded weeks before the Feb. 7 blast, Selk said.
'Ducting used for dust extraction and dust collectors can themselves be conducive to the initiation of dust explosions,' he said.
Selk said investigators haven't yet determined if the dust extraction equipment was working in the part of the refinery where the explosion originated - a basement area with conveyor belts used to transport sugar from three giant storage silos to a nearby packaging area.
On Friday, investigator Phil Durham of the federal Bureau of Alcohol, Tobacco and Firearms said evidence of sugar dust accumulation was found in the basement beneath the silos.
Steve Behm, a spokesman for Imperial Sugar, said he did not know any details of the earlier dust explosion mentioned by Selk.
Investigators also have not determined what ignited the dust to cause the explosion. Selk said the Chemical Safety Board is more concerned with why combustible dust was accumulating inside the refinery.
'Finding the ignition source may be impossible,' Selk said.
The explosion killed eight workers inside the plant, and a ninth worker died at the Joseph M. Still Burn Center at Doctors Hospital in Augusta.