Plymouth firefighters who responded to the scene behind Boyd Hall off Pleasant Street said the trailer was completely on fire when they arrived. They said police officers were the first to arrive and reported a small explosion inside the trailer.

The rig was being used by D.L. King Associates of Amherst to store asbestos and "mastic" construction glue taken on of the building.

The asbestos was already rendered non-toxic, but the firefighters were taking no chances and stayed well back, keeping the fire contained but not trying to put it out.

"You can’t put this kind of fire out with water," said a firefighter.

Thick, black smoke billowed from the trailer, high into the air and was carried toward the southeast by a brisk northwesterly wind.

Deputy Fire Chief Tom Morrison put out a call to hazardous materials teams — called HazMat teams — from around the state.

Meredith and the Central New Hampshire HazMat team were first to arrive and set up a detoxification center off Langdon Street. They used children’s plastic swimming pools to hose down any firefighters who had trouble breathing or felt itching or chemical burning on their skin.

Morrison kept checking his crews to assure they were not suffering skin or eye problems while they waited for foam to arrive.

Plymouth Firefighter Paul McGill was taken from the scene to Speare Memorial Hospital suffering from a rash which was believed to be caused by the heat and not from exposure to any hazardous material, according to Morrison.

"We’re going to use an alcohol-based foam that is resistant to alcohol products," he said. "Besides the asbestos and mastic, the van had vinyl flooring and polyethylene plastics."

Fire crews from Ashland and Campton also responded to back up the Plymouth units.

Plymouth Fire Lt. Casino Clogston said his initial concern was to prevent the fire spreading to Boyd Hall, only a few yards away from the burning trailer.

He said the building in that area has been gutted for renovation with only bricks and steel showing.

About 7:30 a.m. the foam arrived and firefighters wearing breathing apparatus began spraying foam into the still-burning trailer, quickly knocking down the fire and smoke.

Morrison said the Department of Environmental Services and the State Special Investigations Unit were notified to begin the investigation into the cause of the fire and possible side effects of the hazardous materials, if any.