WASHINGTON (From news reports) -- The chemical fire at Inland Empire Paper Co. in Millwood has been out for more than a day but crews from several agencies continued work at the scene Thursday.

Company employees called the Spokane Valley Fire Department after they found a small fire under a storage container around 1 p.m. Wednesday, according to a news release from the mill. The tote contained an additive, sodium hydrosulfide, used to brighten wood pulp, Doug Krapas, the mill's environmental manager, said in the release.

The additive is commonly used as a pulping agent in making paper, textile dyeing and as a food preservative, the company said. The additive can also be flammable if it comes into contact with water, which may have happened Wednesday.

The paper company thanked firefighters for their response and said no employees reported injuries.

A person who answered the company's main phone line Thursday said only "essential people" were at the mill Thursday. Company employees were evacuated and decontaminated Wednesday.

Spokane Valley Fire Department Capt. Scott Crawford said Wednesday a bleaching agent leaked out of an overpressurized container at the mill, 3320 N. Argonne Road in Millwood, and reacted with another chemical, causing the fire. Crawford said firefighters could not extinguish the blaze with water because of the nature of the second chemical.

The fire drew a massive firefighter response to the mill, including Spokane Valley firefighters, the Spokane Fire Department, Spokane County fire districts 8 and 9, paramedics and the Washington state Department of Ecology.

The fire was contained around 3:20 p.m. Wednesday, but efforts to fully manage the remaining chemicals, which smoldered overnight, continued Thursday, according to a Spokane Valley Fire Department news release Thursday.

Hazardous materials crews remained on the scene Thursday.

"Management of an incident of this size and complexity takes an incredible amount of time and coordination of resources," the release said.

Crews and equipment constantly rotated, giving firefighters in personal protective equipment time to rest and decontaminate from the chemicals. Hoses on trucks were cleaned and swapped out.

Unusually high spring temperatures contributed to the complex situation.

Spokane Valley Fire Department spokeswoman Julie Happy said while no employees were injured from the fire, one firefighter was taken to Providence Sacred Heart Medical Center on Wednesday because of the heat. Happy said the firefighter was released from the hospital and returned to work that day.

Happy said two containers were damaged by the fire.

"Incidents of this size and magnitude take a toll on area Firefighters and resources," Spokane Valley Fire Deputy Chief Zack Bond said in the release. "Having good relationships with our neighboring Fire District and public safety agencies is incredibly important for the continued safety of all our Spokane area communities."

The fire department release said the last major hazardous materials incident in the area was in 2007 when Whitley Fuel caught fire in northeast Spokane. The blaze drew about 100 firefighters, caused a neighborhood to evacuate, destroyed the Whitley warehouse and a neighboring towing company and damaged another business.