Five children were pulled to safety from the second-floor balcony of a burning apartment complex in Prince George's County yesterday just minutes before a series of explosions leveled the building.

Two firefighters, one police officer and five residents -- including a man and two women who jumped out of windows -- had to be hospitalized after the two-alarm blaze at the Carriage Hill Apartments in the 3300 block of Curtis Drive in Temple Hills, fire officials said. All were listed in good condition yesterday. Ten other people were treated at the scene for minor injuries.

The casualty count was nearly much worse. Six firefighters who were inside the apartments evacuated just moments before an explosion flattened much of the building, said Capt. Mark Brady, a spokesman for the Prince George's County Fire Department.

"We feel the Prince George's Fire Department is probably the most fortunate fire department on the face of the earth today," Brady said.

The blaze started about 10 a.m. in a first-floor apartment, Brady said. It took 75 firefighters about 90 minutes to extinguish the fire, which destroyed the 12-unit building, he said. Damage was estimated at $1 million.

Investigators were still trying to determine the cause of the blaze late yesterday, but they were looking into the possibility that it could have been fueled by an oxygen canister that one of the residents used for medical purposes, Brady said. Arson is not suspected, he said.

When firefighters arrived, bystanders told them that they feared three children had been trapped on the second or third floor of the building, Brady said. A crew of six firefighters raced through the flame-filled apartments but could not find anyone inside.

Before they could complete the search, however, a small explosion shook the three-story building, forcing the firefighters to evacuate.

The decision to retreat may have saved the firefighters' lives, Brady said. About three minutes later, a much more powerful explosion rocked the building, blowing apart an exterior brick wall that collapsed on top of several cars in an adjoining parking lot.

The force of the blast was so great that it shattered several windows in apartments 50 yards away.

"The ground just shook," said Anthony McCaskill, 29, a neighbor who ran to the scene to help evacuate residents. "It rumbled through the whole entire complex of buildings."

Brady said investigators believe the first blast may have been caused by the oxygen tank. The resulting damage, he said, may have ruptured natural gas lines in the building, leading to the second explosion. "We're leaning strongly toward that scenario," he said.

The three missing children were found soon after. They and two other youngsters escaped about five minutes before the second explosion when residents formed a human chain and grabbed them from a second-floor balcony, neighbors said.

Easter Wade, 70, who lives in that second-floor apartment, said she was taking a shower when her 8-year-old grandson, Marquette Jenkins, told her that a woman was at the door. The woman, who lived downstairs and was carrying a baby girl and a 3-year-old boy, said a fire had broken out and had cut off her route of escape, Wade said.

Wade threw on a robe and grabbed her three grandchildren. Along with the neighbors, they stepped out on the balcony as smoke filled the apartment.

"Lord, there was so much smoke," said Wade, who was later taken to the hospital to be treated for breathing difficulties. "All I could think was: `Get them children out.' "

The fire displaced about 24 families, including residents of a neighboring building that was evacuated when firefighters cut off gas and electricity. Brady said the Red Cross was helping victims. A shelter was set up at Suitland High School.