Watertown firefighters remain at the scene of an overnight fire on the corner of Main Street and Heminway Park Road.
A man's burns suffered last week unveiled a "marijuana butter" making operation in a Watertown apartment.
Police said they responded to a fire at a multi-family home on Main Street back on April 7.
The building had to be evacuated.
Firefighters told police that when they arrived, they found a man with burns on his hands and face.
When investigators entered the building, they found evidence of a "highly sophisticated elaborate setup" for the making of marijuana butane extract, which is also known as "dab" or "marijuana butter."
As a result of the butane factor, they had to treat the building as if it contained hazardous chemicals.
Watertown and state police detectives executed search warrants on the second floor rear apartment of the home.
As of Monday, they said the exact cause of the fire remains unknown.
No other details were released.
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