The deadly sugar refinery blast in Port Wentworth that claimed at least eight lives was caused by a cloud of sugar dust that somehow ignited, said the state's top fire official.

Insurance and Fire Commissioner John Oxendine said the dust could have been ignited by static electricity, equipment or anything that makes a spark.

"With that much sugar dust in the air, think of it this way: If you have a building and the natural gas is turned on, and then something ignites it, the air is filled with natural gas and you're going to have an explosion —- even if you have sprinklers," he said.

The last remnants of the blaze at the Imperial Sugar Co. were doused on Thursday, a week after the fires were ignited. Eight people died in the blast, and firefighters are working to recover the body of another worker who remains missing.

Sugar dust was thought early on to be the cause of the Feb. 7 blast. Emergency crews were able to snuff out the fire at the plant's main building Wednesday, but the blaze persisted in its 80-foot silos until Thursday.

Crews called in a team with powerful equipment to assault the silo fires, where thick masses of molten sugar smoldered even after a helicopter dumped thousands of gallons of water.

The team extinguished the stubborn blazes using a mix of foam and water that lowered the temperatures inside the silos from as high as 4,000 degrees to below 70 degrees, Port Wentworth Fire Chief Greg Long said.

The refinery is located on a 160-acre site on the Savannah River upstream from Savannah. The plant takes up 872,000 square feet, and about 12 percent was destroyed, company spokesman Steve Behm said.

"This was a terrible tragedy," Oxendine said. "My hope is that this information will be of some assistance to family members as they're trying to grieve and go through this process, that they at least have some knowledge of how this occurred."