Three people escaped unharmed early yesterday after a fire was set at their house in Northeast Washington, an attack that authorities said could have been committed by a serial arsonist who has been striking the Washington area for 18 months.

Authorities said the fire was similar to 39 blazes that have been set, taking place outside residences in early morning hours. The fire was the second in four days that fit the pattern of the serial arsonist, they said.

Yesterday's fire took place in the same Northeast neighborhood where a June 2003 arson killed 86-year-old Lou Edna Jones. She is the only person to have died in the attacks, authorities said. More than a dozen people, including one D.C. firefighter, have suffered minor injuries.

Authorities said yesterday's fire was set about 4:50 a.m. outside a one-story house in the 2800 block of 30th Street NE, in the city's Brentwood section. An accelerant was used to ignite the side of the house, they said. In many of the other cases, officials said, accelerants were used to set fires on porches of homes in the hours before dawn.

The fire awakened James Thomas, 29, who said he saw a flickering light outside his bedroom window.

Thomas said he quickly realized that flames were shooting up the side of the house, so he ran outside and began dousing the fire with water from a garden hose. After extinguishing most of the fire, he raced back inside and helped his grandmother and uncle to safety before calling 911, he said.

"It happened so fast," Thomas said. "I'm angry, but I'm happy that I got my family out. There is some damage to the house, but at least we didn't lose it."

Thomas's 75-year-old grandmother, Minnie M. Hodges, said she felt fortunate to have survived. "I feel blessed that my grandson discovered the fire," said Hodges, who is recovering from a recent stroke. "The Lord was with him."

Thomas's uncle, Hubert Hodges, 46, said he, too, felt lucky to be alive. Recovering from hip replacement surgery and other health problems, Hodges said he was not sure he would have survived if his nephew hadn't acted so quickly.

Some of the roof's shingles were singed, and siding was burned and melted. D.C. police and firefighters and investigators from the federal Bureau of Alcohol, Tobacco, Firearms and Explosives combed the house and yard for clues.

A task force of local and federal agencies that has been closely tracking the arson attacks is leading the investigation into the fire, authorities said.

Authorities said it would likely take a tip from the public to solve the case. They have released a composite sketch of a man seen near some fire scenes and are offering a $35,000 reward for information that leads to the arrest and conviction of a suspect. They have posted the sketch and other information on a Web site, www.pgfireems.com.

The fire marked the first time that the serial arsonist is believed to have struck in the District since last November, authorities said. It is the 19th fire under investigation in the District; 18 are being probed in Maryland and three in Virginia. Authorities also are investigating an attempted arson in the District.

The fires within the past week appear to be the first set by the arsonist in the area since June, authorities said. The lull ended on Friday, when a house in Riverdale Park in Prince George's County was set on fire about 4:35 a.m. All eight occupants escaped safely, alerted to the fire by a pair of passing newspaper carriers.

Residents of Brentwood said they were concerned that their neighborhood apparently has now been hit twice, once with fatal consequences. Jones was killed on June 5, 2003, as she slept in an upstairs bedroom of her home in the 2800 block of Evarts Street NE. A small memorial of stuffed animals remains on a fence outside Jones's charred and vacant house.

One Brentwood resident, Charles Lewis, 31, said he was keeping an eye out for strangers and was going to purchase fire extinguishers.

"It makes you a little leery," Lewis said. "It makes you think a lot. It wakes you up."

James Thomas, 29, quickly doused a possible arson attack at his home in Northeast Washington and helped family members to safety.