Fire swept through a Bladensburg apartment complex early yesterday, injuring three men, including one who severed his right arm while leaping through a window to escape the smoke.

The fire, the third major blaze in Prince George's in the last four days, began shortly after 3 a.m., causing an estimated $100,000 in damages and displacing 10 families. The cause of the fire has not been determined.

County fire officials said that an apartment resident, 20-year-old Robert Coske, seriously injured his right arm when he jumped through a plate glass window in his first-floor room. Coske was taken to Union Memorial Hospital in Baltimore, where a spokesman late yesterday said he was in the intensive care unit.

Also injured were tenants John McMillin, 27, who was treated at Prince George's County General Hospital for minor head cuts and released, and John Womeldorf, 29, who suffered from smoke inhalation.

Fire investigator Sgt. John Dennison said the two-alarm blaze apparently began in Coske's bedroom, shot out the window and up to a second floor apartment before snaking into an adjoining unit. The three apartments were completely destroyed. Seven others were damaged by smoke and water before county firefighters finally brought the blaze under control.

"I heard an explosion and that's what woke me up," said Ann Carter, a tenant in a second-floor rear apartment. Carter said she roused her son and they fled into the street. Outside they saw flames shooting out of Coske's apartment, and Coske sprawled on the ground.

Fire investigators said that the exploding sound Carter heard may have been windows popping. After the fire was brought under control, other residents picked through their charred belongings.

"This is my stuff," said Teresa Sampson. Before the fire began, Sampson and a friend had been decorating their apartment for a birthday party. Minutes later, they were fleeing for their lives.

The Bladensburg fire followed two others last week in the county.