RUMFORD – Nine workers at the NewPage Inc. paper mill were injured just after 1 p.m. Thursday by a chemical reaction that exposed them to a chlorine vapor, according to emergency and mill officials.

The company has yet to release the names of the seven men and two women, but Rumford Hospital Nursing Director Jane Aube said late Thursday afternoon that the workers were all in stable condition.

“One employee was definitely exposed, but the others (injured) were in the area or responded to the events,” mill spokesman Tony Lyons said.

Med-Care Director Dean Milligan said that the nine workers had chemical inhalation or respiratory problems, but no one was critically injured.

Aube expected six to be treated and released by evening, but the three others will be hospitalized at least through the night, because they need longer observation and treatment, she said. All were given oxygen and intravenous fluids.

The liquid chemicals involved in the reaction are sodium hypochlorite, a strong bleaching agent that was being transferred inside a beater room in the basement of the North End building, and muriatic acid, also known as hydrochloric acid, a corrosive agent.

The beater room is a preparation area where substances are mixed before going to paper machines, Lyons said.

He said workers were piping one chemical from a 250-gallon plastic drum to another drum containing a different chemical when the accident happened.

During the transfer, Lyons said there was a contamination and a small release of chlorine gas.

“When sodium hypochlorite is mixed with any compound with an acid base, it creates a chemical reaction. We believe the release occurred for less than a minute. There was no spill,” he said.

Barbara Parker, director for the Division of Response Services at the Maine Department of Environmental Protection, said the two chemicals are never mixed together intentionally because it creates an exothermic reaction.

“The chemicals would have gotten hot enough to create a vapor and sputtered and spattered like a fried egg on a pan,” Parker said.

“If inhaled in your lungs, it can burn your lungs. If it touches your skin, it can have the same effect,” she said.

The mixture of the chemicals can also trigger pulmonary edema and convulsions.

The mix was small enough so that the reaction could be contained inside the mill, and there was no danger to the community, officials said.

The nine workers were immediately decontaminated in the mill’s decontamination shower system, Parker said. The decontamination included removal of all clothing and a thorough water rinse.

Rumford Hospital erected its own decontamination tent for hospital staff, wearing protective gear, to triage the patients, before taking them inside the building.

Of the mill’s 300 workers, only 60 in the North End were evacuated through the No. 15 machine building, arriving at the lower gate office area by about 1:40 p.m. Machines in the area were shut down for three to four hours during the evacuation process, but the rest of the mill continued to operate, Lyons said.

Med-Care and Rumford and Mexico firefighters arrived at the mill’s lower gate end shortly after the 1:07 p.m. call for help. Several donned self-contained breathing gear, then were trucked in to the affected area.

For several minutes, emergency responders didn’t know what types of chemicals had been mixed.

“We have nothing in our guidebooks for this type of mixture,” Milligan said during a radio transmission of what responders initially thought was a mixture of hypoammonium and bromide, sodium hypochlorite and muriatic acid.

“This is the first time that we’ve had an incident like this in a long time,” in Oxford County, said Scott Parker, director of the Oxford County Emergency Managment Agency, who responded to the scene. “It’s interesting that it happened now, because we’re having a large- scale training incident on Saturday with all of these same people.”

Lyons said the incoming shift would restart machinery in the area, which was vented and determined safe for workers to return.

The last such incident that he could recall involving employee evacuations was a fire during the winter of 2004 or 2005.