Three D.C. firefighters and an ambulance technician were injured in two separate apartment house fires early yesterday morning.

The first blaze, shortly before 5 a.m., destroyed a first floor apartment in a four-story building at 2653 Stanton Rd. SE, a fire department spokesman said. Several residents of the 20-unit building, who had fled to their balconies, were rescued by firefighters.

One firefighter was injured when a railing broke on a second-floor balcony, a spokesman said, and he fell two stories. Sgt. Douglas Wheeler was treated and released at the Washington Hospital Center. No residents were injured in the blaze, a spokesman said.

The second fire, which began at 6:45 a.m., destroyed a basement apartment of a four-story building at 1805 Belmont Rd. NW, a spokesman said. Ralph Stephens, one of the first firefighters to arrive, was injured after he stepped into a three-foot wide air passage that opens onto the apartment's roof and fell to the second floor.

A Hospital Center spokesman said Stephens suffered a fractured arm and possibly internal injuries. He was listed in fair condition yesterday afternoon.

The two ambulance workers were injured when, during their attempt to assist Stephens, they were overcome by smoke. Both were taken to George Washington University Hospital, where Herbert Roulack was treated and released and ambulance paramedic William Jones was admitted for further observation. He was listed in good condition.

A fire department spokesman said the first fire was accidental but declined comment on its origin. Investigators have not determined the cause of the second blaze, he said, but arson is not suspected. Both fires caused heavy smoke damage.