A fire that killed an Army sergeant and four children at a Fort Eustis apartment complex yesterday apparently was caused by careless smoking, according to a spokesman for the post near Newport News.

Lt. Col. John Carl identified four of the victims as Sgt. Ronald L. Matson, 29; his daughters Pamela, 2, and Christina, 9; and a niece, Amanda Nutting, 7. The fifth victim was believed to be Matson's 6-week-old son, Carl said, but a positive identification had not been made by late Saturday afternoon.

Carl said the base fire department responded to a call from one of Matson's neighbors about 1:20 a.m. yesterday. He said two trucks and eight firefighters arrived to find the apartment engulfed in flames and intense smoke. It took less than two minutes to extinguish the fire, he said.

The victims were taken to McDonald Army Hospital at Fort Eustis. Matson and two of the children were pronounced dead on arrival, Carl said. Efforts to save the other two children were unsuccessful, and they were pronounced dead minutes later in the emergency room.

Carl said Matson's wife, Rhonda L. Matson, was not at home at the time of the fire.