Check out the local report on CNN affiliate WGN-TV.
Chicago (CNN) -- Two Chicago firefighters were killed Wednesday and at least 17 were injured, when a wall and roof collapsed without warning in an abandoned building on the city's south side, the city's fire department said.
None of the injuries was life-threatening, said Fire Commissioner Robert Hoff in an afternoon news conference. One firefighter was in stable condition, he said.
Hoff identified those killed as Corey Ankum, who had been with the department less than two years, and 12-year veteran Edward Stringer. Both were inside the structure. Other firefighters were working the blaze from the roof.
CNN affiliate WGN aired footage of a line of firefighters saluting one body as it arrived at the medical examiner's office later Wednesday.
Chicago Mayor Richard M. Daley said in a statement, "The deaths of Firefighters Stringer and Ankum are both a sad reminder of how much gratitude we owe our first responders and a tragedy for all Chicagoans."
The deaths came on the 100th anniversary of the Chicago Stockyards fire, which killed 21 firefighters and the city fire marshal.
The fire was reported shortly before 7 a.m. in the office area of a commercial building on East 75th Street, said Larry Langford, spokesman for the Chicago Fire Department.
The routine fire call became a multiple-alarm blaze after part of the roof collapsed as firefighters were inside, he said. Four firefighters were trapped after the collapse occurred, and two of them died from their injuries, Langford said.
The building was boarded up in the front but the back was open, leading firefighters to think that homeless people may have sought shelter there, Hoff said.
The cause of the fire is under investigation, Hoff said.
Investigators will look at whether ice or weather was a factor, as well as the age of the building and its heavy roof, the commissioner said.
"There are things that happen when buildings are aged, and that could have been one of the contributing factors in this case," Hoff said.
The fire in the building's northeast corner had been brought under control, Hoff said, and firefighters were working on hot spots and "looking for homeless or vagrant people" when the collapse occurred.
A wall of the building collapsed into an alley, Langford said, bringing part of the roof down with it.
A search of the rubble found no one else, Langford said. Heavy equipment was being brought in to take the building apart.
He said it was his understanding that both of the fallen firefighters had children. While the loss of a firefighter is always a tragedy, he said, "it's been compounded" by the deaths occurring so close to the holidays.
Another firefighter died recently while battling a downtown blaze, he said.
CNN's Sara Pratley contributed to this report.