The Boston Fire Department reports a stove fire erupted around noon in a duplex at 120 Southern Ave.
All the occupants of the building got outside safely, but two firefighters were taken to Brigham and Women's Hospital with burns.
The fire went to three alarms because of the intense heat in the building, the department says, adding firefighters were rotated in and out of the building because of the heat.
The fire did an estimated $150,000 damage, the department says.
On Saturday, another three-alarm fire damaged three homes on Speedwell Street.