Searchers in helicopters scoured the one square mile area of the mudslide yesterday. Authorities were also trying to determine how to get rescuers on the ground safely, said fire chief Travis Hots, who described the mudflow as “like quicksand”.
“We suspect that people are out there, but it’s far too dangerous to get responders out there on that mudflow,” he said. Officials described the slide as “a big wall of mud and debris” that blocked about one mile of State Route 530 near the town of Oso, about 55 miles north of Seattle. It was reported to be about 60ft deep in some areas.
Several people – including an infant – were critically injured and as many as 30 houses were destroyed.
Mr Hots said the number of missing could change because some people may have been in cars and on roads when the slide hit on Saturday.
The mud was so thick and deep that searchers turned back late on Saturday after attempting to reach an area where voices were heard crying for help. Rescuers could not hear any signs of life once they got closer. The slide blocked the North Fork of the Stillaguamish River, which prompted an evacuation notice because water was rising rapidly behind the debris. Authorities were worried about severe downstream flooding if water suddenly broke through the debris.
The Snohomish county sheriff’s office reported that two people had been killed at the scene. Authorities later said one of the people who had been rescued died at a hospital.
A six-month-old boy and an 81-year-old man remained in critical condition yesterday at Harborview Medical Center in Seattle. Hospital spokeswoman Susan Gregg said two men, aged 37 and 58, were in a serious condition, while a 25-year-old woman was upgraded to satisfactory condition.
Five of the injured were taken to Cascade Valley Hospital in Arlington, and one has been treated and released, hospital spokeswoman Jennifer Egger said. She did not know the condition of the others.
The American Red Cross set up at the hospital, and evacuation shelters were created at Post Middle School in Arlington and the Darrington Community Center.
One eyewitness said that he was driving on the road and had to quickly brake to avoid the mudslide.
“I just saw the darkness coming across the road. Everything was gone in three seconds,” Paulo Falcao said.
The National Weather Service issued a flash flood watch for Snohomish County, while Washington governor Jay Inslee also proclaimed a state of emergency.
Authorities believe the slide was caused by ground water saturation from recent heavy rainfall. John Pennington from the Snohomish County Department of Emergency Management said the area has a history of unstable land. He said a slide also happened there in 2006.
Mr Pennington said the slide happened without warning. “This slide came out of nowhere,” he said.