NASHUA, N.H. (AP) — A natural gas leak led to an explosion and fire at a mental health center in New Hampshire on Monday, injuring three firefighters while all occupants managed to evacuate safely.

About 40 people were in the Greater Nashua Mental Health facility when the alert was triggered due to a reported odor of gas. Despite ongoing investigations by firefighters, an explosion occurred, causing part of the building to collapse according to State Fire Marshal Sean Toomey.

The injured firefighters were transported to a nearby hospital, where they were treated for non-life-threatening injuries. Local authorities responded promptly by alerting nearby residents to extinguish flames and prepare for potential evacuation.

Jesci Larochelle, a local resident living less than half a mile from the explosion site, reported that she felt her home shake as if a tree had fallen. She began checking for damage immediately after receiving the alert.

The Greater Nashua Mental Health center, known for its services related to substance misuse and support for deaf and elderly clients, is located in a commercial area of Nashua, which is about 45 miles north of Boston.

Aerial footage revealed considerable destruction at the site, with flames and smoke billowing from the wreckage and debris scattered around the area. Governor Kelly Ayotte expressed her gratitude to the heroic efforts of firefighters and first responders.

The incident is further complicated by ongoing cold weather conditions in the Northeast, affecting firefighting efforts, as mentioned by Nashua Fire Chief Steve Buxton. Similar incidents in the past have raised concerns about safety, notably a gas explosion in a Pennsylvania nursing home that resulted in fatalities.