Firefighters responded to the Eden Memorial Park Cemetery on West Irving Road around 4 p.m.
Officials said it started on the second floor, and while people were in the chapel at the time they were able to get out safely.
"I was in my office working upstairs. I just smelled something, but we had people working on the roof today so I assumed it was something on the roof," said Nancy Wolski, cemetery office manager.
Fire officials said when they arrived on the scene, heavy smoke was coming out of all four sides of the building, which was the area contractors had begun working to replace Wednesday morning.
"They actually went out to lunch, didn't know there was any damage," said Jim Battista, co-owner of Eden Memorial Park Cemetery. "When they came back they saw smoke coming from underneath the eaves."
Keenly aware of the sacredness of the space, even as flames tore through the roof, a few firefighters rushed in to try to salvage any bit of written memory.
"We actually did stop some of the water at one point, went in and used tarps to try to protect the records," said Batallion Chief Mike Cesaretti, Schiller Park Fire Department.
"It's pretty sad but we're going to rebuild," Battista said. "We're going to put it back together, whatever it takes."
Chopper 7HD was live over the scene, where the chapel's roof appeared to have collapsed due to the fire.
The Schiller Park Fire Department said there were no injuries yet reported. The cause of the fire is not yet known.