Both victims were found in a first-floor unit where the fire apparently started, MacDonald said.
Crews were ordered out of the building about 45 minutes after they arrived at the 18-unit brick building shortly before 8 p.m., Deputy Fire Chief Joseph Finn said.
The blaze apparently started in a kitchen. Within minutes, flames spread to all five floors.
Flames shot out from the roof nearly three hours after the fire was reported, as some of the 130 firefighters sprayed water from ladders. The fire was still smoldering Tuesday morning, MacDonald said.
In Milwaukee, a duplex fire also killed two people, but a family of eight was able to escape, said First Battalion Chief Randall Zingler. After leaving an upper unit, the family knocked on doors and windows trying to wake up the two people in the lower apartment, Zingler said. That fire also started in the kitchen.