SPRINGFIELD, Mass. (AP) _ Fire spread through a house early Monday, killing five members of a family, including a teen-ager whose body was found near a container of gasoline. A sixth relative saved her life by diving from a second-floor window.

''Flames were coming out of every single window of the house,'' when the first truck arrived about two minutes after the 2:12 a.m. alarm, said Deputy Fire Chief Patrick Keough.

The five victims were identified as Barbara Ann McKoy, 39; her son, Gerald, 19; her daughter, Renee, 16, and grandchildren Cassandra McKoy, 2, and Joseph Blanks, 3, fire department spokesman Giorg Placanico said.

Authorities are awaiting the results of an autopsy on the body of Gerald McKoy, whose body was found in a downstairs den near a partially melted plastic container of gasoline, before commenting on how the fire might have started, said District Fire Chief George C. Nadeau.

''There is nothing conclusive,'' Nadeau said. ''The origin of the fire was in the living room and den area.''

The only survivor was Mrs. McKoy's other daughter Barbara Annette Blanks, 20, the mother of Joseph. She jumped to safety after she was roused by her mother and found the stairs blocked by flames, said Placanico.

She was treated at a hospital and released, according to a nursing supervisor.

Investigators were searching for the cause of the fire. Keough said the flames were so intense that ''at the present they have not been able to determine where or how the fire started.''

''The neighbors heard what they thought was an explosion, but that apparently was the windows cracking,'' Keough said. ''A fire generally smoulders for a while, but once the windows blow and it gets oxygen it can just start roaring.''

Neighbor James Lewis, 24, said he awoke and ran across the street to the burning house.

''I tried to kick in the front door, but it wouldn't give. I kept hearing screams from upstairs,'' Lewis said. ''I ran to the back and got into the kitchen, but I couldn't see a thing. The smoke was so thick.''

The fire was the worst in the Connecticut River city of 152,000 people since five people died in an apartment fire on March 27, 1980, officials said.