Rescuers aided by dogs, sonar equipment and aircraft were still trying to find trapped survivors in Oso, a remote town north of Seattle, Snohomish County sheriff's spokeswoman Shari Ireton said.
With six bodies found Monday, the toll from Saturday's disaster north of Seattle grew to 14 dead, Snohomish County Emergency Management Director John Pennington said Monday at a news conference.
Though rescue teams will keep looking for survivors, Pennington said it's less likely by the day that anybody will be found alive.
"We as a community, as a county ... are moving toward a recovery operation," he said.
Snohomish County Fire District 21 Chief Travis Hots told reporters that "the situation is very grim."
"We're holding out hope, but keep in mind we've not found anybody alive on this pile since Saturday," he said.
Pennington said the number of people unaccounted for ballooned from 18 on Sunday to 108 on Monday and, near the end of the day, to 176. He stressed that's a list of names, not a tally of anticipated fatalities.
Pennington said he expects that number to drop "dramatically" because people will turn up and the process of gathering names is inexact, with some duplicated information. Seven people are reported injured.
To help with the effort, California is sending 18 urban search and rescue personnel to Washington, California Gov. Jerry Brown said late Monday.
The landslide covered about a square mile and was caused by groundwater saturation tied to heavy rain in the area over the past month. It affected Oso, with a population of about 180, and Darrington, a town of about 1,350.
Dave Norman, a Washington state geologist, said the landslide was about 4,400 feet wide with a wide debris field.
"This is one of the biggest landslides I have ever seen," Norman said.
Authorities grew concerned Monday that another slide could occur and suspended the search for a few hours. After geologists determined the threat was low, the search resumed.
The affected area includes 35 traditionally built houses, 13 manufactured homes and RVs and a cabin, Pennington told reporters. Pennington said 25 structures were occupied full time, and the others were occupied part time, perhaps as vacation homes.
Pennington said the slide's occurrence over a weekend was more challenging for rescuers because more people were apt to be home than on a weekday. Victims could also include "contractors and other workers" in the neighborhood as well as others who were "driving by," he said.
Authorities have worked feverishly to find survivors.
"Total devastation. I mean, it's just unbelievable. It reminds me of what a tornado looks like when it's touched the ground," Snohomish County Sheriff Ty Trenary said.
At one point, he pointed at a pile of muddy rubble.
"You can tell from the debris this appears to be part of somebody's kitchen, the inside of the house," he said.
While there's a tremendous effort to rescue people who may be trapped, Hots said Sunday that the rescue operation must be focused on keeping responders safe because the area is highly unstable.
The mud flow is like quicksand, he said. The landslide is 15 feet deep in some places.
Caroline Neal hopes her missing father, Steven, 52, will still be rescued. He's a plumber who was on a service call when the land gave way.
"My dad is a quick thinker, and he is someone who takes action in an emergency," Neal told CNN affiliate KING. "If he had any warning at all, we just have to think he is somewhere and he's safe and they just can't reach him right now.
On Saturday, rescuers dug through the rubble while survivors cried for help underneath debris. Rescuers heard voices around 11:30 p.m. and considered trying to reach the possible survivor or survivors, but "the mud was too thick and deep," Hots told reporters.
"Mother Nature holds the cards here on the ability of ground personnel to enter the slide area. It is essentially a slurry," Washington Gov. Jay Inslee told reporters Sunday.
He called the rescue operation "aggressive."
"Every human endeavor ... is being explored here to rescue and find their loved ones," the governor said.
Inslee added that some rescuers had gotten "caught ... up to their armpits" in the slide and "had to be dragged out by ropes."
John Lovick, a county executive, addressed a reporter's question about whether voices were still being heard.
"We were told that there were noises in that area," Lovick said, stressing that fire chief Hots had decided that it was "too risky" to place rescuers in that area. "We are not hearing any reports of people hearing voices today or after last night."
Inslee said he received assurance from Federal Emergency Management Agency officials Monday morning that assistance is on the way.
FEMA Regional Administrator Kenneth Murphy told the governor in a phone call that he was providing a "verbal emergency declaration" that will allow for immediate federal assistance, the governor's office said in a news release.
In the nation's capital, U.S. Sen. Patty Murray of Washington state told her colleagues the damage was hard to imagine.
"There are dozens and dozens of families who do not know if their loved ones are still alive," she said. "This weekend I saw some of the worst devastation I have ever seen in my home state."
On Monday, Harborview Medical Center reported treating five patients. Four are in the intensive care unit: a 22-week-old boy and three men, ages 37, 58 and 81. The child is in critical condition, and the adults are in serious condition, the hospital said. A 25-year-old woman was also reported in satisfactory condition at the hospital.
Cascade Valley Hospital said six patients were brought there. One was listed in stable condition, one was transferred to another hospital, and four people were treated and released, the hospital said.
The landslide cut off State Road 530 to Darrington. Part of the Stillaguamish River also was blocked, and residents were warned of possible flooding both upstream and downstream of the collapse.
The Washington State Patrol provided photos that showed floodwaters and sprawling debris covering a rural patch of the road, framed by woodlands and snow-capped mountains.