SEATTLE -- Seattle firefighters are investigating whether an arson fire in the U-District Monday is related to two other fires deliberately set nearby in the last three days.

The latest fire was set Monday night in an alley behind Brooklyn Avenue Northeast near Northeast 52nd Street.

The two fires on Saturday happened within two blocks to the west and six blocks to the north in relation to Monday's fire.

In each case, the fires were set using discarded furniture.

Monday's fire started at 8:30 p.m. in an old couch, burned up a staircase and then ignited a fence and some plants above it. The flames were heading toward a nearby house before firefighters extinguished the flames.

Jake Clifford, who lives in the nearby house, said he noticed something odd about the couch just before the weekend.

"It slowly collected trash and rubbish and I came back maybe four days ago and somebody wrote on it 'burn me now,'" said Clifford.

On Saturday, firefighters responded to an occupied apartment house near Northeast 55th Street and 15th Avenue Northeast at 7:55 p.m. Someone ignited a discarded couch behind the building.

The fire burned nearly to the roof, partially blocking the rear exit.

Minutes later, someone lit mattresses and other discarded items in the alley behind Brooklyn Avenue Northeast and Northeast 56th Street.

Fire investigators think those two incidents may be related.

The Seattle Fire Department said there's no suspect information yet in any of the arsons.