Four coughing and screaming children trapped alone in a burning apartment in Reston were rescued yesterday by firefighters who broke down the locked door with a sledgehammer and crawled through smoke-filled rooms to reach them.

Pam Weiger, a spokeswoman for the Fairfax County Fire and Rescue Department, said three of the children -- ages 1, 4 and 6 -- were treated for smoke inhalation at Access emergency medical center, and released. The fourth, Jason Murray, 3, was taken to Fairfax Hospital and admitted to the pediatric intensive care unit, where he was reported in stable condition.

The mother of the children, Brenda L. Murray, told fire officials she had left the apartment, at 11655 Stone View Square, for a few minutes to borrow some laundry detergent from her mother, who lives in another building in the complex, Weiger said. While she was gone, the 6-year-old set the living room sofa on fire while playing with a cigarette lighter, Weiger said.

The fire was reported by Erik Evans, who lives next door, after he and his roommate saw smoke coming from behind their kitchen cabinets. Evans said that he tried to break down the door, but failed.

"I saw a kid with his hand in the window. I didn't see his face," said Evans. "I made a motion for him to lay down."

Capt. Billy Walter, one of the firefighters who rescued the children, said the children were screaming when firefighters entered the apartment.

James Blackburn was the first firefighter in, Walter said, and found a child in the front bedroom. Walter said he found the 1-year-old on the floor against the door in another bedroom "crying, gagging and coughing."

Another firefighter found a third child in the same room, lying on a bed near a window. The last child was found by a fourth firefighter in the third bedroom.

Walter said the firefighters reached the apartment "quicker than normal" because they received the call on the way to the fire station from another call. Officials estimated that the firefighters arrived at the apartment four to five minutes after receiving the call.

The smoke detector in the apartment was ringing when firefighters arrived, Walter said. The mother of the children returned home about 10 minutes after the fire started.

Weiger said the fire caused $15,000 to $20,000 damage, most due to the heavy smoke generated from the overstuffed sofa and chairs in the living room.