Oklahoma City firefighters say a woman and four children are dead after a blaze at a house on the city's northwest side.

City Fire Department Maj. Tammy McKinney says the children killed in the Wednesday morning fire range in age from 2 to 8 years old. McKinney says a man also is in critical condition at a local hospital.

KOKH-TV reported that four of the victims were children and were related to each other.

McKinney says the home was already engulfed in flames when firefighters arrived just minutes after receiving a call around 6:30 a.m. The cause of the blaze was not immediately known. McKinney says the home did not have working smoke detectors.

He says the interior of the home about a mile east of Lake Hefner in northwest Oklahoma City appears completely gutted by the fire.

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The Associated Press contributed to this report