CHICAGO (CBS) — A man and a woman were found dead in a house fire early Monday in west suburban Addison.

A passerby spotted flames in a one-story single-family home in the 700 block of South Ellsworth around 2:30 a.m. and called 911.

Firefighters arrived within five minutes, but the fire already was out of control, with flames shooting through the roof.

The roof collapsed during the blaze, and when firefighters eventually got inside, they found a man and a woman dead inside.

Firefighters believe one or both victims were disabled. Crews found a handicap license plate at the scene, as well as a walker near the woman’s body.

Addison Fire Protection District Deputy Chief Scott Walker said there were no smoke detectors in the home; a working detector might have saved the victims’ lives.

“It’s extremely hard. The hardest part is we – not just Addison, but most fire districts and fire departments – we spend a lot of time trying to get word out about smoke detectors, fire safety. No matter how much time we spend, there’s always a house that seems to get missed, or people don’t listen to what we’re saying,” Walker said.

The victims’ names have not been released.

The house was gutted. The cause of the fire was under investigation, but it did not appear to be suspicious. Firefighters believe it started in the kitchen.