RUMFORD – A young Mexico girl with asthma appears to be the only person who was affected late Tuesday afternoon by one of two accidental releases of noncombustible but odorous gases from NewPage Inc., mill and emergency officials said Wednesday.

Citing patient confidentiality laws, Med-Care Ambulance Director Dean Milligan declined to name the 12-year-old girl. She was initially treated for breathing difficulties outside her apartment in Mexico, then taken to Rumford Hospital. It was not immediately known if she was treated and released.

At 4:42 p.m. Tuesday, Mexico firefighters were sent to 14 Holman Ave. after a strong sulfur smell was reported.

Fire Chief Gary Wentzell said Wednesday afternoon that the girl was with others outside an apartment and didn’t look very well, so he called for assistance from Med-Care.

About 40 minutes prior, Osgood Avenue residents and several children, a Mexico patrolman and Dixfield officer, and two Med-Care crews who responded to a car-bicycle accident at the intersection of Osgood and Brown street, all noticed and remarked about the smell, wondering aloud if it was from the mill.

An approaching thunderstorm kept the smell concentrated and close to ground rather than dispersing it.

Wentzell said the odor was initially believed to be from sulfur-based off-gassing from the mill. But mill spokesman Tony Lyons said Wednesday that it wasn’t sulfur because the mill doesn’t use sulfite.

He said each accidental release of a mixture of gases lasted two minutes. It happened in the pulp mill section. The first occurred at 11 a.m.; the second, at 4 p.m.

Normally, “we collect all the smelly gases and rout them to boilers and incinerate them,” he said. It’s part of the mill’s $60 million legacy that was spent on environmental projects, which removed the so-called paper mill smell, Lyons added.

But, gases were vented Tuesday during the pulping process in what are called “batch digesters,” when that equipment was being emptied.

“We have a number of things going on at once in that system and we were trying to do a heat recovery project. We not only incinerate gases, but we collect and recover heat and save it. This was rare and unusual,” Lyons said of the accident.

He also said the vented gas did not violate any laws, but he couldn’t name the gases involved.

“We knew it was happening at 11 and 4, and people took care of it. There was no interruption to production,” he added.

It was the third known accidental incident at the Rumford paper mill in less than three weeks.

On May 17, nine paperworkers were injured just after 1 p.m. by a chemical reaction that exposed them to a chlorine vapor, mill and emergency officials said. Of the mill’s 300 workers, 60 in the North End were evacuated from the affected area.

The liquid chemicals involved were sodium hypochlorite, a strong bleaching agent that was being transferred inside an area where substances are mixed, and muriatic acid, also known as hydrochloric acid, a corrosive agent.

Workers were piping one chemical from a 250-gallon plastic drum into another drum containing a different chemical. They’re not supposed to be mixed together.

That accident is being investigated by the Occupational Health and Safety Administration in Augusta, a supervisor said by phone Wednesday afternoon.

On May 24, while emergency responders were at the mill for a critique session regarding responses to the May 17 incident, a pulp-mill valve failed, causing a smaller-scale evacuation.

, Milligan and Lyons said. There were no injuries.

“It was an internal mill event and, we chose to evacuate a very small portion of the pulp mill. It was a very isolated incident,” Lyons said.