Firefighters look over the situation Tuesday on Chester Street in North Cambridge. (Photo: Cambridge Fire Department via Twitter)

Around 40 people were displaced, most briefly, and one person found dead after a fire broke out early Tuesday in one apartment of a four-story, 29-unit building at 15 Chester St., North Cambridge.

Cambridge firefighters, police and Pro EMS ambulances responded to the building at approximately 4:41 a.m., where several witnesses “reported a loud explosion followed by a heavy volume of fire,” city spokesman Jeremey Warnick said.

It ultimately rose to a three-alarm fire, according to the report, but the main body of the fire had been knocked by down by 5:14 a.m., according to scanner reports. By shortly after 8 a.m. all fire companies had cleared the scene except for investigators from Cambridge fire and police and a State Police fire unit. The cause of the fire has not been determined and remains under investigation, Warnick said.

The sole occupant of one, top-floor unit was found dead by firefighters before 5 a.m., and one Cambridge firefighter was taken to a local hospital with non-life-threatening injuries. Red Cross was on the scene to help with displaced residents, Warnick said. (By the afternoon, the number of displaced people had been lowered to 15 by local spokespeople and Jake Wark, public information officer for the state’s Department of Fire Services.)

Much of the 1965 brick building, which is paired on the lot with another 29-unit building, will be habitable after a cleanup, as the fire was contained to the one apartment, according to fire officials.

The same building was in the news Aug. 24 when a joint fugitive investigation led to the arrest there of John Hallett, 54, a Cambridge man suspected of murdering and dismembering his roommate in Indiana in 2017.