An early-morning fire in the stairwell of a Mount Rainier apartment building yesterday has been added to the list of arsons under investigation by a regional task force, officials said.

The blaze broke out about 12:55 a.m. in the stairwell between the second and third floors of a Kaywood Gardens apartment building in the 4200 block of Russell Avenue. It appeared that some sort of fuel had been used to set the blaze, Prince George's County fire officials said.

No one was injured in the fire, but five people had to be rescued by firefighters, including four who escaped through an open window and down a firetruck ladder. Damage was estimated at about $10,000.

Fire officials said they linked the blaze to 38 other suspicious fires set in the Washington region because of certain similarities: the fires were set with a liquid accelerant in the early morning hours and were set in the staircases or near the doors of occupied dwellings.

One person has died and nearly a dozen have been injured in the string of fires, which started in March 2003. Most of the fires were set in Prince George's County and the District.

"We're trying to get away from saying fires are linked, versus similar in nature, to the ones under investigation by the task force, but this case has been added to the list of cases that the arson task force is investigating," said Capt. Chauncey Bowers, a spokesman for the Prince George's County Fire/EMS Department. "This is the 39th fire."

A year ago, fire officials first noticed similarities in a series of blazes under investigation in the county and the District. Local fire departments formed a task force of investigators and detectives to sift through evidence and search for the perpetrator.

In March, police arrested a Riverdale Heights man after he appeared at two schools pretending to be a fire investigator. Noel Gibson, 33, was indicted on a felony charge of lying to a federal agent. But his fingerprints did not match those found at fire scenes, and he was in jail when the next blaze linked to the serial arsonist was set April 16 in Oxon Hill. Gibson remains in custody.

About a month later, May 13, another fire was set in the Hybla Valley area of Fairfax County.

Yesterday's fire came a month and two days after the Hybla Valley fire. Flames charred the top portion of the stairwell, leaving a blackened wall and ceiling and an ashy mess on the floors.

Residents of the apartment building, one of many identical buildings in the complex, said they noticed the fire just before 1 a.m. Dana Donnell, 26, said she heard a rustling sound outside her second-floor apartment and went to open the door.

"When I opened my door, it was just flames," she said.

Donnell retreated into the apartment. "I tried to decide," 'Am I going to go window, or am I going to go door again,' " she said. She chose the door and rushed past the flames to safety.

Donnell said the fire was set directly under the stairwell's fire extinguisher and was set in a way that trapped third-floor residents in their apartments.

"Look at the hallway as being a giant furnace," said John Tresvant, 50, who lives in a third-floor apartment. " . . . The fire was so intense it sealed my door shut. As a matter of fact, it sealed all the doors on this floor shut."

He escaped through a window.

On the first floor, Ibrahima and Angela Barry smelled gasoline and then heard somebody outside calling the fire department on a cell phone. Ibrahima, 34, rushed upstairs to warn neighbors, but he was driven out by the smoke and flames. He called the fire "the work of the devil."

"A full-fledged human being would reason, a human being would not do that," he said.

He said his Christian faith gives him confidence that the arsonist will be caught. "Whatever is done in darkness," he said, "must come to light."

Anyone with information about the fire can call the arson task force at 301-77-ARSON.