The flames were contained to the room where the fire started on the south end of the hotel and no one was injured, according to Fire Media Affairs Director Larry Langford, who said there was "very heavy" smoke on the fourth floor.
"I was in a very deep sleep, [then] I heard the alarm," said Jerry Quigley, 45, a custodial worker who lives in the building. "I could smell the smoke and by the time I had grabbed some important papers and got to my door, the smoke just billowed in."
Emma Rolon, 55, who routinely sleeps in her clothes in case there is a fire, said she "saw red flames on the outside of the building on the fourth floor" after she heard fire alarms going off.
Most of the rooms were not damaged by the fire and will be habitable, however, as of 5:30 a.m., the fire department was not allowing residents to re-enter the building because the fire damaged the alarm system, according to Langford, who said people will not be allowed back in until the system is repaired.
One or two rooms may be uninhabitable due to fire damage, Langford added. A witness on the scene said the windows of the unit where the fire was burning are broken out and the area around them is blackened.
The fire was struck out at 4:54 a.m., the director said.
He estimated the building housed about 40 units in all.
About 125 fire department personnel were on the scene, according to Fire Media Affairs spokesman Kevin MacGregor.
The large and quick personnel response was due in part to the fact that the building is old and that many of the residents have medical problems. In addition, fresh memories of the fire at the Paxton Hotel, which killed 19 people and injured 31 more in 1993 just a block away from the Carling at 1432 N. LaSalle, prompted the extra response, Langford said.
The cause of the fire is under investigation early Wednesday.
The STNG Wire contributed to this report.