Authorities are investigating whether an early morning fire at a house in the Franconia area of Fairfax County yesterday is linked to a string of 39 suspicious fires across the region that began 17 months ago.

Yesterday, a neighbor across the street from the house, Dennis Engel, 54, said he noticed "a glow to the front door" of the house in the 4000 block of Elmwood Drive as he was leaving for work.

"There was smoke coming out from the eaves and seeping through the siding" of the one-story rambler, Engel said. Fire officials arrived within minutes of Engel's 911 call at 5:45 a.m.

The owner, Rogelio Reyes, had left that morning for work and the house was empty.

The fire began on the left side of the door and burned upward into a V-shape pattern, causing $7,500 in damage, said Lt. Raul Castillo, spokesman for the Fairfax County Fire and Rescue Department.

If authorities conclude that the Elmwood Drive fire was started by the serial arsonist, it would be the third Fairfax blaze linked to the string. The others were in February and May.

One person has died and nearly a dozen people 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. About a year ago, fire officials first noticed similarities in a series of blazes under investigation in those jurisdictions. Local fire departments formed a task force of investigators and detectives in June 2003 to sift through evidence and search for the perpetrator. Most of the blazes were set at similar times of day and using similar methods on the exteriors of homes.

In yesterday's fire, Engel said the garden hose was missing from Reyes's front yard, so he tried to stretch his hose across the street, but it did not reach. He and his 19-year-old son circled the burning house looking for a point of entry or other damage but did not find anything.

Engel, a security officer for the U.S. House of Representatives, left for work by 6:05 a.m.

Investigators are interviewing neighbors from the Burgundy Village subdivision and other potential witnesses at nearby locations, such as gas stations. They are also conducting lab tests on evidence collected from the house.

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