NAUGATUCK, Conn. (WTNH) — Firefighters in Naugatuck were battling a fire at a vacant warehouse on Water Street Monday night, according to the Naugatuck Fire Department.

Officials said the fire was reported at 6:10 p.m. at 238 Water Street. The building was previously used to make airplane parts and was once owned by Lewis Engineering, according to fire crews.

Mutual aid was provided by the Waterbury and Middlebury fire departments.

Crews used defensive operations in their efforts to extinguish the blaze and poured water on the building from the outside. Rain is also crediting with helping put it out.

The fire was extinguished by Tuesday morning.

Naugatuck Assistant Fire Chief Walter Seaman spoke with News 8 about why the building burned for so long.

“I think the construction of the building. The type of materials it is. It’s a masonry exterior and it has timber interior for framing devices,” Seaman said. “This is a very very large building, known as a mill building. We do have three aerials in operation. We went defensive. That means we pulled all interior crews out and we are putting water on it from the exterior.”

The Metro North train was stopped briefly because of the fire.

Two homes were evacuated due to smoke conditions but have since been able to return, according to fire officials.

“The smoke was everywhere,” said Kelvin Mitchell, who lives nearby. “It got to a point where you couldn’t even see like five feet in front of you.”

The Connecticut Department of Energy and Environmental Protection (DEEP) was on the scene to conduct air monitoring tests.

Fire officials plan to demolish the building.

“Right night, the building is structurally unsound,” Naugatuck Deputy Fire Chief Ken Hanks said. “We’ve already had some partial walls collapse, the entire roof has collapsed.”

Police have a warrant to search the building before it’s torn down as part of the investigation into the fire. A cause has not yet been determined.

Police are asking people to avoid Water Street while demolition continues on the building.