AYER -- The cause of an early morning tire fire Monday at J.P. Routhier & Sons' tire recycling facility on Willow Road in Ayer remains under investigation.

Ayer Fire Chief Robert Pedrazzi said the call came in just before 4 a.m. Quickly, the fire in an outdoor stockpile of shredded tire bits became fully involved.

The cause is "undermined at this time," Pedrazzi said. "We're looking at a few different things."

Firefighters from several towns were called in to assist, including crews from Shirley, Littleton, Devens, Harvard, Groton, and Westford.

A hydrant near the tire yard was used, as well as a second hydrant about 1,500 feet away.

"We had a long hose lay. We had 3,000 feet of our own," Pedrazzi said. "Groton came over and finished off with a reel truck."

A newly purchased foam trailer from the Mid-State Fire Mutual Aid Association, housed in the Holden Fire Department was brought in. Pedrazzi said the trailer was loaded with 500 gallons of foam, with 65 extra gallons to load. All of it was used, including foam provided by the Devens, Fitchburg, Ashby, Gardner, and Westford fire departments.

"That's what we use to put the fire out because it was a flammable-liquids fire that you can't put out with water," Pedrazzi said.

"We had 100 gallons that we used ourselves. We keep a lot on hand because we have a lot of places that have rubber, with the big industrial base, but 100 gallons isn't anywhere near enough to put out a fire like that," he said.

Liquefied petroleum-based tires and foam streams were channeled into catch basins on site and were sopped up Monday afternoon. Pedrazzi estimated the scrap tire pile was 25 feet to 30 feet high and covered about an 80-square-foot area.

Business owner Paul Routhier repeatedly jumped into excavator equipment to move the pile to assist the fire departments.

"We needed him to move the machine because it was at risk of catching fire," Pedrazzi said.

Routhier would hop back onto the machine "on and off, when we needed him to move the stuff," said Pedrazzi.

Pedrazzi said the weather helped the firefighters.

"The way the wind was blowing, it was blowing the smoke all away from us. We were lucky. It was going straight up and over and all going away from us," Pedrazzi said.

Crews cleared the scene at 11 a.m. There were no injuries reported. The state fire marshal's office dispatched a recovery truck to provide relief to the firefighters battling the blaze. State and federal environmental officials and the company's previously retained licensed site professional were at the scene to investigate.

It was not immediately clear if the fire scene is above the town's Zone 2 aquifer protection district, according to Pedrazzi, DPW Superintendent Dan Nason and Board of Health Chairman Mary Spinner.

Routhier's tire reclamation facility is between two PanAm Railway properties on either side of Willow Road. On the western side of Willow Road and directly abutting Routhier's facility is a vacant, paved parking lot that used to serve as a new-car, train-to-truck transfer facility for PanAm. That vacant lot is not located above the Zone 2 water supply.

PanAm operations began over the past year despite prior court challenges posed by the town of Ayer regarding risks potentially posed to the town's primary drinking water source. Monitoring wells have been installed to try to detect any contamination due to PanAm operations.

The Routhier company is the only tire-reclamation facility of its kind permitted by the Massachusetts Department of Environmental Protection, according to the company's website. The company states it processes more than 6 million tires per year into tire-derived materials.

The Ayer Fire Department has been straight out during this new fiscal year. The department has already fought two significant brush fires straddling the Ayer-Groton town lines in July. He said he'll be briefing town selectmen on the overtime his department has already consumed this year.

"I've spent a lot of time. This year's not starting off good," Pedrazzi said. 

"This one wasn't as long... the weeklong brush fire killed me. It was eight days and it was all day, every day."

Pedrazzi's noted the department has responded to 60 more calls so far this year than at the same time last year. "I don't know why we're so busy," he said.