Firefighters responded to a fire at 103 Newton St. just after 11:30 a.m. Saturday morning.
Lt. Thomas Paquin of the Holyoke Fire Department told CBS 3 that when crews first arrived, fire was visible out of the first and second floor windows.
Paquin said the cause of the fire was a malfunctioning gas-fired space heater.
The three people who live in the building got out OK, but will have to stay with relatives for the time being.
A next-door neighbor has also been displaced temporarily due to smoke damage.
The neighbor is being assisted by the American Red Cross.
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