Three investigators examined the site but were unable to pinpoint what started the blaze, Department of Public Safety spokesman Steve McCausland said.
Firefighters from 17 departments responded to the fire at Grimmel Industries, a metal recycling yard in the former Pejepscot paper mill that has burned four times in the last nine years.
The fire began around 3 a.m. Tuesday and was extinguished around noon, said Shawn Larrabee, deputy chief of the Topsham Fire Department. He said no one was working at the site when the fire began, and no one was injured.
The fire began in a pile of metal scrap and destroyed three empty buildings, he said. Many of the other departments responding to the blaze sent tanker trucks because the fire blocked access to the Androscoggin River.
``Every time we come here it's a very difficult fire to put out,'' Larrabee said.
Officials from the Sagadahoc County Emergency Management Authority were called to assist firefighters and to ensure that potentially contaminated runoff from the fire scene did not run into the river, Director Rusty Robertson said.
Firefighters from 20 towns responded to a 2002 fire at the metal recycling plant in which a two-story pile of recyclable materials and a small building burned.
Styrofoam and other materials in the subbasement of an outbuilding caught fire in 1999.
A 1995 fire at the former paper mill that caused more than $1 million in damages was ruled to be arson after fire investigators tested samples of rubble from the century-old building along the Androscoggin.
Fire departments responding on Tuesday included Harpswell, Cundy's Harbor, Durham, Pownal, Woolwich, Georgetown, Richmond, Yarmouth, Freeport, Falmouth, North Yarmouth, Lisbon, Bowdoin, Bowdoinham, West Bath, Bath, and Brunswick.
