AURORA, Illinois - Some residents jumped from their windows to escape flames as a fire ripped through a suburban Chicago apartment building early Sunday, leaving six dead and a dozen others injured.

At least 35 people lived in the three-story building in suburban Aurora, where the fire started about 4 am Sunday, city public information officer Dan Ferrelli said in a statement. Three of those killed were children.

Several residents said they were forced to jump from their windows as the fire tore through their apartments.

"We were just afraid and I had a hard time breathing so I opened the door to my room and smoke started to come in and I just ripped out my window and jumped out with a little son," Elva Renteria told The Chicago Tribune. She escaped with her 1-year-old son.

Two children and a man were pronounced dead at hospitals, and another child and two women were declared dead at the scene, Ferrelli said. The children who died were a boy about 10 years old, a boy estimated at 5 to 7 years old and an infant, he said.

About a dozen others were taken to hospitals; two were treated and released. Aurora, about 40 miles (64 kilometers) west of Chicago, is Illinois' second biggest city.

According to a preliminary investigation, the fire started on the building's first floor and spread through an open door to a common hallway, trapping residents on the second and third floors.

Ferrelli said the cause of the fire is under investigation.

Fire officials and the building's owner said there were working smoke detectors in the building.