The report released Tuesday was submitted earlier in the week to the Arkansas Department of Environmental Quality.
The fire prompted authorities to evacuate 2,500 people from the area around the Teris LLC hazardous-waste storage warehouse. No injuries were reported, however, and the evacuees were allowed to return to their homes and businesses a day later.
The report says waste materials shipped to Teris LLC in December from a New York rail yard contained more than just the soil and sodium chlorate _ a common herbicide and oxidizer _ that workers expected. The waste may have contained enough wood, creosote and fuel residue to react with the sodium chlorate to produce heat.
"From the initial investigation, it appears there was some foreign material in there that caused the reaction,'' Teris vice president Doug Riley said.
Barrels of the same material caught fire Jan. 12 after they were removed from the smoldering warehouse and stored temporarily in a trailer on the Teris grounds.
The Jan. 2 fire smoldered for days after firefighters chose not to fight it for fear that water would react dangerously with some of the stored chemicals.
The Teris facility, formerly operated by Ensco, disposes of hazardous wastes from industries and government operations. The plant receives spent solvents, waste oils, chlorinated hydrocarbons, herbicides and insecticides, as well as dirt, residues and contaminated water from cleanup activities from other sites.
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