Fire and police crews swarmed a home on Carlisle Road in the aftermath of a heavy fire, possibly due to an explosion.
"We are still investigating the cause," said Nashua Deputy Fire Chief Michael O'Brien Jr., standing outside 7 Carlisle Road.
The right half of the house was completely charred and exposed as smoke rose from the building.
It was not yet known if anyone was inside, O'Brien said.
"We consider every building to be occupied until we do our search," O'Brien said.
Crews were readying to check the home for structural soundness prior to a search.
Police were also on the scene and a member of the city's fire marshal's office was stretching out yellow crime scene tape from the edge of the property.
A source at the scene said that an off-duty firefighter was home when a possible explosion ignited the house.
A group of police detectives arrived at the scene just about 3:30 p.m.
Check back for updates as we get them.
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