Authorities and residents along a tree-lined river north of Seattle were bracing for flooding Saturday night after a massive mudslide in the morning killed at least three people, leveled at least six homes and left a muddy mix of debris in the river that was acting as a dam.
Authorities worry that water could build up behind that dam of debris and mud and then cause flooding if it breaks through.
Emergency responders from the U.S. Navy, fire departments and law enforcement agencies across the region were searching through dusk for additional victims and clearing debris, the Snohomish County Sheriff's Department said.
Two of those killed were found dead at the scene; a third person died at a hospital. Their identities were not immediately released.
Harborview Medical Center in Seattle reported that a 6-month-old baby boy was in critical condition at the hospital along with a 58-year-old man and an 81-year-old man. A 37-year-old man was in serious condition, and the status of a fourth injured man was unknown.
At Cascade Valley Hospital in Arlington, four patients remained hospitalized, three of them with minor injuries. One patient had already been treated and released, spokeswoman Jennifer Egger told the Los Angeles Times.
Skagit Valley Hospital was treating a 68-year-old man with fractures in the lower part of his body.
The mudslide, which happened at about 10:45 a.m., was estimated to be at least 45-by-60 yards, officials said Saturday afternoon. A statement from the county attributed the mudslide to heavy rain in the last month.
The homes destroyed were in a community along the Stillaguamish River in Arlington, about 40 miles north of Seattle. Snohomish County officials said they were strongly urging some residents along the river to voluntarily evacuate because of fears that the river would overflow.
The National Weather Service issued a flood warning for the area near Arlington, but said "massive flooding" was unlikely.
State Highway 530, a two-lane road, was closed for seven miles from Oso Loop to Little French Creek Road, the Washington Department of Transportation said.
The agency said its experts on the terrain were flying to Oso to advise county crews.