New Boston, NH – A Nashua house painter died Tuesday morning after an explosion and fire at a newly constructed home where he was working.

Antonio De Souza, 46, of Nashua, was alone at the house on Foxberry Drive, according to Danielle Cole, a district chief for the state Fire Marshal’s Office.

A neighbor and an off-duty firefighter were able to make contact with De Souza, who told them he was injured. But the two couldn’t hear him after the explosion and were pushed back by the flames, Cole said.

The blast happened just before 10:30 a.m. and could be heard as far away as Francestown and Lyndeborough, which are about 15 miles away, Cole said.

“We had multiple 911 calls from around town,” Police Chief Jim Brace said.

Cole said the cause of the explosion remains under investigation; authorities are examining the propane system in the home.

When fire crews arrived, they found the house fully engulfed in flames, Cole said.The bottom level had collapsed, bringing the second floor down on top of it.

Though debris flew hundreds of feet, damage was confined to the house, Cole said.

Neighbors were allowed to stay in their homes as firefighters worked to put out the blaze.

With the second floor and roof sitting on top of the collapsed first floor, Fire Chief Dan MacDonald said it was a challenge getting to the heart of the fire. The blaze was under control in about 45 minutes.

Lori Kyer, a state bail commissioner, said she was at the town’s police department when the explosion happened.

“We all heard this giant explosion,” she said, adding that the windows and doors all shook.

Kyer said she followed fire crews to the scene.

“When I arrived, the entire first floor of the house was completely collapsed,” she said.

Hours later, firefighters were still working on putting out hot spots, MacDonald said. Hoses had to be stretched about 3,000 feet to the house.

“We have to get water where we can get it,” MacDonald said.

More than a half-dozen communities responded to provide mutual aid for New Boston, including Bedford, Manchester, Francestown, Mont Vernon, Weare, Bedford, Brookline, Dunbarton, Henniker and Milford.

The house was for sale and had not yet been assigned a street number, Cole said.

An autopsy is scheduled for Thursday to determine De Souza’s cause of death.