OSO — Residents of the North Fork of the Stillaguamish River are being advised to evacuate, by the Snohomish County Sheriff’s Office, in the wake of three confirmed deaths as a result of a landslide on Saturday, March 22, across State Route 530, between Arlington and Darrington, as a National Weather Service Flash Flood Warning for the area remains in effect through Sunday, March 23.

The landslide was first reported around 10:45 a.m. on March 22, at the 29400 block of State Route 530, near milepost 37, and at least six houses have been confirmed destroyed.

According to Shari Ireton, director of communications for the Snohomish County Sheriff’s Office, the cause of the slide is believed to be ground water saturation, from heavy rainfall in the area previously in the month, but they’re still assessing how many other structures may have been affected. Identification of the victims is pending from the Snohomish County Medical Examiner.

The slide has cut off Darrington and is blocking the North Fork of the Stillaguamish River at Whitman Road. Initial reports indicate the slide is at least 45 yards wide and 60 yards across. Both directions of State Route 530, between mileposts 37 and 38, are completely closed as a result, and the public is being asked to avoid the area.

Several emergency response crews have since been dispatched, including members of not only the Snohomish County Sheriff’s Office, but also the Washington State Patrol, Department of Transportation, Department of Emergency Management, U.S. Navy and most of the fire service agencies in north Snohomish County.

One helicopter with the Snohomish County Sheriff’s Office has been transporting victims, while the other helicopter has been surveying the area from the air for the Department of Emergency Management. Among those transported from the area have been at least eight adults, and one 6-month-old child, to local hospitals.

Upstream of the landslide, the North Fork of the Stillaguamish River will likely flood low-lying areas, including roads and possibly some homes. When and if the landslide-induced blockage releases, some flooding downstream to Arlington is possible.

Do not drive cars, vans or trucks through flooded areas, as this is the cause of most flood-related deaths in Washington.

The city of Arlington activated its Emergency Operations Center at 2:30 p.m. on March 22, in response to the landslide. City staff have since been monitoring events upstream on the Stillaguamish River.