LAKEWOOD, Colo. (CBS4) – Investigators want to know what caused a fire that sent a man to the hospital Friday morning.

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The fire happened in Lakewood on 18 South Chase Drive and put firefighters in danger.

(credit: CBS)

(credit: CBS)

The flames went through the roof and it collapsed while firefighters were inside. Fortunately none them were injured. But when the house caught fire at about 2:30 a.m., a 17-year-old neighbor may have saved lives by calling 911.

“My daughter answers the door and sees he’s in his underwear and goes in to get a blanket for him,” neighbor Josh Menck said.

West Metro Fire said the blaze began in the basement.

“This fire burned for a fair amount of time before anyone was alerted to this fire,” Josh Smith with West Metro Fire said.

Fire investigators believe smoke detectors didn’t work in the house.

“From my understanding they are too old, over 10 years,” Smith said.

The family told fire investigators batteries were put in recently.

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“Again, they didn’t test the detector to make sure that it worked still,” Smith said.

Firefighters also want people to know that clutter found inside the home creates a danger for everyone.

“It can make a fire definitely hotter because there’s more stuff to burn inside the building.”

An 85-year-old woman and her two sons escaped the house, but not without someone taking a risk.

“The one victim that was transported to the hospital entered the building two more times after he got out, and we never recommend you going back into a building that’s on fire.”

Neighbors believe the man was trying to rescue his cats. Meanwhile a father is proud his daughter called 911, possibly saving lives.

“Yeah it is pretty cool, I’m very proud of her,” Menck said.

The condition of the man sent to the hospital is unknown. It’s likely he suffered smoke inhalation.

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The cause of the fire may not be known for several weeks.