By Jeremy Ross

CREST HILL, Ill. (CBS) — A young boy was killed and his mother critically injured in a fire in a southwest suburban apartment complex early Saturday.

Firefighters received a call for the fire around 3:30 a.m. Saturday and were on the scene at the Woodlands Apartment Complex in Crest Hill about five minutes later.

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When they arrived, first responders say they saw smoke coming between two apartments in a three-story, 36 unit apartment building.

They found an unconscious woman in one unit and her son, between one to three years old, there as well.

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Police say the young boy was eventually pronounced dead and the woman was taken to a burn unit.

“The fire was quickly controlled and it appeared to mostly burn itself out,” said Fire Chief Dave Skoryi of the Lockport Township Fore Protection District. “There is a smoke detector located in the apartment. Due to the extreme heat, we are unable to determine if it was working properly at this time.”

The mother remains in critical condition with burns to her body.

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Investigators are working to determine the cause of the fire.