Excerpts from abc7chicago.com:

Chicago fire officials said a blaze started shortly after 3 p.m. Monday afternoon in the 800-block of West Gunnison Street and was struck out around 6:30 p.m., though crews remained at the scene to battle hot spots. The damage to the building is such that relocation of residents will be required.

“Our companies had a hard time getting water on the fire due to the fact that it was in the rear of the structure, and we couldn’t get right up on it,” said Assistant Deputy Fire Commissioner of Operations Barry Garr.

Residents said someone was working on the building’s plumbing in the basement. Firefighters smashed top floor windows, temporarily feeding the fire to then try and contain it. Hours into the losing battle fire ate away at the roof.

“That’s when you heard the horns sound and everything indicating to the firemen, ‘Drop what you’re doing and get out. I don’t like what I see,'” Garr said.

A CFD battalion chief was hit on the head by falling debris, he was wearing a helmet at the time, and was taken to Northwestern Memorial Hospital in stable condition. No residents were injured.