A 32-year-old Alexandria woman was killed, three girls were seriously injured and about 20 people were forced from their homes early yesterday when fire swept through an Alexandria apartment building.

Gloria Jean Johnson of the 400 block of East Monroe Avenue in Alexandria's Rosemont section died after having heart failure when the apartment building where she lived caught fire about 3:30 a.m.

Two girls believed to be her daughters were rescued from the burning building by firefighters after incurring cardiac arrest. Last night, a 13-year-old was in the intensive care unit of Alexandria Hospital and a 10-year-old was listed in critical condition in Children's Hospital of Washington.

A 12-year-old girl who was not believed to be related to the dead woman as listed in fair condition in Children's Hospital.

Jane Davidson, a spokesman for the Alexandria Fire Department, said that fire officials had not determined the cause of the blaze but that damage to the nine-unit building was estimated at $125,000. She said that all the building's occupants had been temporarily relocated.

Davidson said that unusually dense smoke made the fire especially difficult to fight. Five ambulances and and seven fire trucks were sent in to quell the blaze. No firefighters were injured.