ST. AGATHA — An explosion of undetermined origin destroyed a garage-warehouse and an attached two-story house Thursday night, causing more than $250,000 in damage.

Insurance investigators, according to the owner of the building, will be on the scene of the Main Street fire today to investigate the cause of the explosion heard by people living in the home attached to the warehouse.

Carl Michaud, the owner of Michaud’s Furniture and Michaud’s Funeral Homes of St. Agatha and Frenchville, has owned the building for about one year. He said the structure was insured.

More than 50 firefighters from four volunteer fire departments assisted in the effort to extinguish the flames. The firefighters fought the blaze for about five and a half hours. Some crew members were at the scene throughout the night on fire surveillance duty. Assisting St. Agatha firefighters were firefighters and equipment from Frenchville, Sinclair and Guerrette.

Six vehicles were destroyed, including trucks and tractors used by Michaud in the several businesses he owns, and at least one automobile.

“I called the other fire departments as soon as I saw the fire,” St. Agatha Chief Gerard Castonguay said Friday. “I knew it would be bad.”

Philip Thibeault of Madawaska was visiting his mother, who lives across the street from the Michaud complex, when he saw smoke coming from the building and called the fire department.

Richard Ringuette, who lives with his wife, Terry, in the house attached to the warehouse complex, heard an explosion before smoke started coming into the home, according to Castonguay. The explosion was said to be in the garage area of the building.

The Ringuettes were able to leave the building safely.

Castonguay said he believed it was gas or gas fumes that were ignited by some spark. The fire marshal was called, said the chief, but no investigation was needed because there was nothing suspicious about the fire.

In the Ringuette home, fire destroyed the second floor and attic area, and smoke and water destroyed the first floor. The Ringuettes lost everything they owned, said Castonguay.

There were no injuries reported.