An unattended candle started the raging fire that killed three people in a Fairfax County condominium Sunday, fire investigators said yesterday.

The fire that broke out at 5:20 a.m. killed Sadia B. Mohammed, 69, her daughter, Anisa A. Yassin, 36, and a family friend who was staying with them that weekend, Iftu J. Salah, 16.

Mohammed's son, Hassen K. Beshir, 35, jumped from a third-floor balcony to escape the flames. He remained in critical condition in the burn unit at Washington Hospital Center yesterday, a hospital spokesman said.

Two other residents were treated for smoke inhalation but otherwise refused medical treatment, fire officials said.

The candle, which was left burning on a ground-floor patio, eventually set nearby papers and boxes alight and then spread to the vinyl siding, said Lt. Mark D. Stone, a county fire department spokesman.

The fire quickly shot up the three stories of the condominium, a building consisting of four semi-detached units that each contain six apartments.

Fire officials said 18 of the 24 units in the building on Mary Caroline Circle, in the Franconia section of the county, are still uninhabitable. The three-alarm blaze caused an estimated $9 million in damage.

Stone said the entire building might have to be vacated in order to rebuild, but that would be up to the insurers and the condominium owners. County and Red Cross officials were assisting residents.

County fire investigators pieced together the cause through witness interviews and an analysis of the burn patterns, Stone said.

Stone said the building was built before sprinklers were required. He said the department is assuming that smoke detectors in the units worked normally unless the investigation proves otherwise. Some residents said they did not hear the detectors. Others said they did.

There were 401,000 residential fires in the nation in 2002, according to the U.S. Fire Administration. The fires caused 2,695 deaths, 14,050 injuries and $6 billion in damage.

Cooking was responsible for the greatest number of residential fires, 21 percent.

Open flames, such as a candle, embers or a torch, caused 5.7 percent of fires.

Fairfax County firefighters use a truck ladder Sunday to reach a third-floor unit on Mary Caroline Circle. Three people were killed in the fire.