Investigators concluded that sugar dust likely fueled an August 1998 explosion at the company's refinery in Sugar Land, Texas.
Two people were hurt, including a worker burned over nearly half of his body.
A Sugar Land Fire Department report stated that a dust collector in the fourth-floor blast area "was stopped up with sugar."
A related department report cited "a large accumulation of powdered sugar on the floor and on the building structural components."
Such conditions resemble those federal investigators say they found at Imperial's Port Wentworth, Ga., refinery, which exploded and burned on Feb. 7, 2008. Fourteen people were killed, and many more were injured. Many of the victims were treated at Augusta's Joseph M. Still Burn Center at Doctors Hospital.
On Thursday, however, Imperial rejected the fire department's findings and said that since 1998, it has spent millions of dollars to upgrade safety.
It also noted the Sugar Land explosion was in the refinery's powder mill area and said the Port Wentworth blasts were in other parts of the plant.
The U.S. Occupational Safety and Health Administration has concluded that sugar dust buildup helped cause the Port Wentworth calamity.
Some 39 lawsuits contending that Imperial failed to eliminate hazards - especially buildup of sugar dust - at the plant are pending in Georgia. A similar suit has been filed in Texas.
In addition, OSHA is seeking $8.8 million for more than 200 alleged safety violations at the Port Wentworth plant and at Imperial's refinery in Gramercy, La. The company is appealing.
The agency has not ruled out the possibility of seeking criminal prosecution of the company or Imperial officials.
At the time of the Port Wentworth catastrophe, company spokesman Steve Behm said Imperial had "completed much ... work" to reduce dust hazards there.
The Savannah Morning News obtained the fire department documents from the city of Sugar Land under Texas open records law.
The city provided the documents shortly after revelations that experts had warned Imperial about sugar dust control problems. The warnings - issued in 2006, 2007 and 2008 - were first reported by the Savannah Morning News.
The company said it did not review one consultant's report until after the inferno at Port Wentworth. It also said none of the experts told them sugar dust posed "any hazards" there.