Fire Department spokeswoman Helen Fitzpatrick says department arson investigators are meeting Tuesday with a 24-member national response team from the federal Bureau of Alcohol Tobacco Firearms and Explosives.

It will help process evidence to find the person responsible for setting one fire early Sunday at a condo complex that was under construction.

That was the biggest of a dozen fires, with damage likely to exceed $1 million.

The quiet night follows two very busy nights for Seattle firefighters. Four more deliberately-set fires were reported early Monday, the latest in a string of weekend arsons that caused hundreds of thousands of dollars in damage in north Seattle.

There are now 13 confirmed arsons.

Fire Department spokeswoman Helen Fitzpatrick said small fires were set overnight Sunday at two garages and on a piece of furniture on a parking strip. Damage from the garage fires did not appear extensive.

Another small fire was extinguished Monday morning at a paper recycling business, the Salvage Broker, in north Seattle. Damage there was minimal, Fitzpatrick said.

There were seven other fires in north Seattle between Saturday night and early Sunday; at least five of those were arson. They burned at a cafe, two homes, a garage and a car dealership.

A condominium complex on Phinney Ridge also burned, but Monday afternoon police said the cause is still under investigation. It has not been labeled arson yet.

The fires came one week after a fire destroyed an apartment building being built in the Wallingford neighborhood, causing $2.75 million in damage.

Mayor Greg Nickels, Fire Chief Gregory Dean and Police Chief Gil Kerlikowske told a news conference Sunday that police would be keeping an eye on construction sites throughout the city. Police also urged people to pick up any trash or other combustible material from their property.

"We're not going to speculate on who this might be," Nickels said. "But we will find them and we will bring them to justice."

The string of fires began when an electrical fire broke out late Saturday night at a University District home. Three people were there when the fire started; two jumped 12 feet from the back roof to escape and another climbed out a basement window, but no one was hurt, Fitzpatrick said.

The fire spread to the roof of a neighboring house before firefighters doused it. The fire is considered an accident.

Less than an hour later, firefighters responded to the fully engulfed condominium complex under construction on Phinney Ridge, near Woodland Park Zoo. Witnesses reported flames leaping 100 feet into the air from the structure, which took up the better part of a city block.

Firefighters evacuated people from nearby homes, some of which had paint blistered by the heat.

The structure remained unstable Sunday and officials were unable to investigate a potential cause or estimate the cost of the damage, which was extensive.

Five deliberately set fires were subsequently reported early Sunday in the Lake City area. Cafe Long on Lake City Way sustained $200,000 in damage, and damage at a Ford dealership near the cafe was estimated $30,000.

A fire in a garage caused $20,000 in damage, Fitzpatrick said, and debris fires at two construction sites totaled $2,000.

Bellevue, Kirkland and Shoreline fire departments pitched in to help.

"The amount of fire activity put a severe strain on our resources," Fitzpatrick said.

The mayor set up a hot line and urged witnesses to call with tips, 800-55-ARSON.

Arsonists have also been at work in the Everett area recently, with two deliberately set fires reported in a multifamily apartment building Sunday morning. No one was injured in those fires.