SEATTLE -- Another fire has been set in Seattle's Greenwood neighborhood, the fourth fire since Sunday night.

The newest fire is at a convenience store at Greenwood Avenue North and North 81st Street, said KIRO 7 Eyewitness News reporter Jeff Dubois.

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A witness told Dubois the store's owner opened the door and smelled smoke. He said it appeared someone folded up cardboard and shoved it into a vent on the back of the building.

Three other fires -- at two separate locations -- were set overnight, firefighters said.

Fire Department spokeswoman Dana Vander Houwen said two fires were set at about 11 p.m. Sunday behind a commercial building near North 77th Street and Greenwood Ave North.

Callers to 911 reported the smell of smoke in the area, and when fire crews arrived they discovered fire set in two places behind a boutique and photo lab.

The fires caused about $1,000 damage before they were put out.

Vander Houwen said another fire was reported by an arson patrol in the area that smelled smoke about 4 a.m. Monday. It caused about $20,000 damage to the back wall of a restaurant, the Olive You on Greenwood Avenue North near North 85th Street.

Arson patrols are out in the area after a string of intentionally set fires in the past several weeks in the Greenwood neighborhood. Vander Houwen said there have been five fires in the neighborhood in two weeks and other fires were reported there in June and August.

The worst was a fire on Oct. 23 that destroyed four restaurants and cause $2 million damage.

Police area leading the arson investigation.