A natural gas explosion is believed to have caused a three-alarm fire at 440 Amherst St. on the afternoon of Feb. 2. Courtesy photo/Jeffrey Hastings

NASHUA – Three firefighters were injured while responding to a four-alarm fire at 440 Amherst St. on the afternoon of Feb. 2.

Although the incident remains under investigation, falling ice may have ruptured a natural gas line.

According to the state Fire Marshal’s Office, the incident was called in at 2:15 p.m. At that time, the reporting caller said there was an “odor of gas and a hissing sound.” Approximately 60 people were initially in the building; however, many of them evacuated before firefighters arrived.

“As the information came into dispatch, it was clear we had a quickly evolving incident,” said Emily Martuscello, director of Emergency Management, during a press conference on Feb. 3. “It escalated very quickly.”

A cell phone alert was also sent out to area residents asking them to turn off burners and put out open flames.

The gutted remains of the Greater Nashua Mental Health Center at 440 Amherst St. following a four-alarm fire on Feb. 2. Telegraph photo by CHRISTOPHER ROBERSON

The gas line exploded minutes after firefighters arrived causing the building, which houses the Greater Nashua Mental Health Center, to become almost completely involved.

“The explosion itself actually knocked the brick facade off of a good portion of the building,” said Fire Chief Steven Buxton. “That’s a pretty tremendous force.”

Firefighters were ordered to evacuate and fight the fire from the outside.

Amherst Street was closed between Somerset Parkway at Thornton Road.

The blaze was brought under control by 6 p.m. However, the building is a total loss, according to authorities.

Mayor James Donchess said this is the third large emergency the city has responded to in the past five months. He said the prior two incidents included the shooting at Sky Meadow County Club on Sept. 20, 2025 and the six-alarm fire on Vine Street on Dec. 2.

“In all three of these cases, our emergency personnel worked very effectively together,” he said.

Gov. Kelly Ayotte and her husband, Joseph Daley, also offered their condolences.

“I have been briefed on the tragic explosion that occurred in Nashua by the Department of Safety and local emergency response personnel,” she said. “Joe and I are praying for those injured and unaccounted for and we are thankful for the heroic efforts by the Nashua Fire Department and first responders on the scene.”

The property is owned by the Community Council of Nashua, NH, Inc. and is valued at $2.5 million.