An apartment complex fire fueled by a gas line explosion left 11 families homeless and five firefighters injured in Chillum early yesterday, according to Prince George's County fire department spokesmen.

Twenty-one other families living in the apartment building will be without heat for at least two days as a result of the fire.

Nine engine companies and six trucks needed 45 minutes to suppress the 6:24 a.m. blaze, which caused damage from the basement to the roof of a section of the LaSalle Apartments on 16th Avenue, said spokesman Jim Mundy.

As firefighters were entering the building to search for occupants, a leaking gas line caused an explosion. John Sullivan, a 19-year-old volunteer fireman, sustained second degree burns on his hands and face, a department spokesman said, and was admitted to the Washington Hospital Center. Four other firefighters sustained minor injuries, Turner said.

Sullivan and another firefighter were at the main entrance of the brick and wood structure when "just as they were going in the explosion blew both of them out of the door," said Hyattsville station chief Keith Moltrup.

Ladder trucks were used to rescue residents from their balconies.

Prince George's County Red Cross spokesman Dave Barringer said 10 of the families were relocated in unaffected sections of the complex by 3 p.m. yesterday, and that the Red Cross supplied them with cots and air mattresses.

According to Mundy, workmen were unable to repair damaged gas lines, and 21 families in the building will be without heat for at least two days.

Damage was placed at $100,000, but Mundy said the figure could rise substantially. Authorities have not determined the cause or origin of the fire.