Excerpts from Fox32chicago.com:

A space heater likely caused a fire that killed a mother and her four young children Wednesday in Des Plaines is the assessment of city fire officials, whose preliminary investigation shows the blaze started at the top of the stairs to a second-floor unit — the only exit from the unit where the family was found. The investigation is now focused on how the heater might have ignited the fire.

There were no working smoke detectors on the second floort. Initial findings don’t point to foul play.

Autopsies by the medical examiner’s office ruled the deaths an accident, saying they died of thermal and inhalation injuries from the fire.