Hope of finding any more survivors are fading following a mudslide so devastating it was picked up by equipment that usually detect earthquakes. At least 14 people were killed as the mudslide smashed through the small community of Oso, about 55 miles (90km) north of Seattle, on Saturday morning.
Around 30 homes were destroyed and dozens more damaged as much of the riverside village was swept away. Rescue workers have sifted through mucky rubble with dogs, helicopters and heavy equipment, as relatives of the missing scoured the debris with their bare hands.
The threat of potential flash floods or another landslide also loomed over rescuers, adding to their sense of urgency.
"Family members are grieving, trying to focus on finding missing loved ones or working through the process of rebuilding what was lost" said Washington State Governor Jay Inslee.
The number of those possibly missing has grown dramatically to include not just residents, but visitors, contractors and people who might have been driving by when the wall of mud and rocks crashed through the neighbourhood.
Relatives were clinging to hope but officials were not optimistic.
"The situation is very grim" Snohomish County Fire District 21 Chief Travis Hots said, stressing that authorities are still in rescue mode and are holding out hope.
But he noted "We have not found anyone alive on this pile since Saturday".
The mudslide blocked a mile-long stretch of road as well as sweeping through the village. Researchers said the size of the affected area is staggering - an area 1,500 feet wide (457m) to 600 feet (182m) tall.
Kate Allstadt, a research seismologist at the University of Washington said readings were similar to an earthquake, but recorded in a different manner.
"The main event left a really unstable cliff. And then lots of small landslides keep falling off," Ms. Allstadt said.
When analysed, this signal could provide details about the amount of earth that moved. Meanwhile desperate families gathered in the tight-knit community.
A boy (4), Jacob Spiller, was rescued and reunited with his mother, who was not at home. But his brother, Jovan, known as JoJo, his father and other members of his family remain unaccounted for.
Jacob Spiller (4) was rescued & reunited with his mother
Rescuers found a chocolate Labrador named Buddy alive, and helped pull the dog from the rubble. It is believed the mudslide was caused by heavy rain that left the ground unstable.
Rescuers pulled this dog from wreckage
A scientist who documented the landslide conditions on the hillside that buckled had warned in a 1999 report filed with the US Army Corps of Engineers of "the potential for a large catastrophic failure", The Seattle Times reported late Monday.
That report was written by geomorphologist Daniel Miller and his wife, Lynne Rodgers Miller. "We've known it would happen at some point," Mr. Miller told the newspaper.
US President Barack Obama, who is in Europe for a meeting with world leaders, has signed an emergency declaration ordering US government assistance to supplement state and local relief efforts.
Locals cannot believe the scale of the destruction.
