CHELSEA (CBS) — An unidentified man in his 80s was found dead in a Chelsea apartment Sunday. Police said the man was found after firefighters put out a fire on the third floor of a multi-family house on Chestnut Street.

The fire erupted just before 2 p.m. on Sunday afternoon.

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Crews were notified about the fire through an activated alarm, according to Police Chief Brian Keyes.

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Chelsea firefighters responded to Chestnut Street on Sunday (WBZ-TV)

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The cause of the man’s death is not known at this time. It is unclear how the fire started.