LYNNWOOD — It could be weeks before investigators determine what may have caused Wednesday’s three-alarm fire in Lynnwood.

The blaze destroyed two apartment complexes, one that was under construction and another where people were living. People were forced out of two other complexes in the area. As many as 150 people were displaced at the height of the fire, according to official estimates.

The fire was reported about 9:30 p.m. at The Reserve senior apartments at Scriber Lake Road and 198th Street SW. Despite intense efforts by crews, flames spread to the 36-unit Lynnview apartment building. It burned for several hours, and hot spots continued Thursday.

The American Red Cross housed 21 displaced residents overnight, including children. Trinity Lutheran Church along 196th Street SW often steps up to provide emergency shelter, said Chuck Morrison, the Red Cross director for Snohomish County.

Some families are likely to stay there until the weekend, he said. Other families, some of whom have renters’ insurance, have found temporary housing.

In addition, one firefighter from Lynnwood and another from Fire District 1 suffered minor injuries at the scene. They were treated and released from a local hospital, city spokeswoman Julie Moore said.

As the fire burned, the orange glow could be seen for miles. Hundreds of onlookers gathered in parking lots and along Scriber Lake Road. As many as 45 fire trucks were on scene at one point, from as far away as Lake Stevens and Monroe, Moore said.

Ash floated down and left a gray coating on cars. Some businesses on the corner of Highway 99 and 196th Street SW used pressure washers to remove the soot.

Investigators are asking witnesses to come forward, including anyone who took photos or videos, Deputy Police Chief Jim Nelson said Thursday. The federal Bureau of Alcohol, Tobacco, Firearms and Explosives is providing assistance to the police and fire departments.

Tips can be submitted to the police department’s website or to detective Brian Jorgensen at 425-670-5632.

It was the second fire at the Lynnview apartments in recent years. A deep fryer sparked the blaze in 2010 that caused $3 million in damage.

Wednesday’s fire also blew out windows at the Picket Hill condos along 200th Street SW. People were allowed to retrieve belongings, but it may take time before the building is livable, Moore said.

Residents did return to the Tanglewood Apartments, which also had been evacuated.

Power outages related to the fire were ongoing Thursday, affecting homes and businesses, according to the Snohomish County Public Utility District.

The Reserve was five stories tall and designed to contain a total of 296 units for seniors. The apartments were supposed to open this fall. Crews had been installing the siding and had not yet gotten to the drywall, Moore said. The developer is based in California.

Because of the amount of water used for the firefighting, property owners in Lynnwood may see discolored water from their taps. The city advised them to let the water run to flush it out.

Scriber Lake Road could remain closed for some time.

“They have started their investigation but they have a long way to go,” Moore said.

Reporter Noah Haglund contributed to this story.

Rikki King: 425-339-3449; rking@heraldnet.com. Twitter: @rikkiking.

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