Firefighters battled flames at the Yankee Castings company in Enfield on Tuesday night, after fighting a smaller fire earlier in the day.
The aluminum, magnesium and bronze casting foundry is located on Shaker Road.
On Tuesday morning, firefighters said it took about 20 minutes to get the fire under control. Many of the employees were sent home, and the fire was believed to be accidental.
On Tuesday evening, before 9 p.m., firefighters returned to the building after flames broke out again.
"There was a hole in the roof. There could have been embers up there. There was a lot of air there. That roof was built in the 1960s and it's pretty dried out," said Mark Zarcaro, of the Enfield Fire Department.
Officials said about 100 firefighters responded to the fire on Tuesday night.
No injuries have been reported, according to the fire department.
On Tuesday night, multiple towns helped Enfield, including Somers, Ellington, and Tolland because of the intensity of the flames.
It is unclear what sparked the fire in the first place. Fire officials said they believe at least a portion of the building will have to be torn down.
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