"We're expecting that number to go up throughout the day," Snohomish County Fire District 21 Chief Travis Hots said Tuesday.
Dozens of people remain unaccounted for. Authorities are working off a list of 176 potentially missing people, though many of those names likely are duplicates and they think that number will decrease.
Snohomish County Emergency Management Director John Pennington said officials expect to have an updated list later Tuesday.
The landslide Saturday destroyed a small community 55 miles northeast of Seattle, flattening about two dozen homes and critically injuring several people.
From the beginning, rescue crews on the ground have faced dangerous and unpredictable conditions as they navigated quicksand-like mud that was 15 feet deep in some places. Some who went in got caught up to their armpits in the thick, sticky sludge.
A scientist who documented the landslide conditions on the hillside that buckled had warned in a 1999 report filed with the U.S. 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 J. Miller and his wife, Lynne Rodgers Miller. "We've known it would happen at some point," Daniel Miller told the newspaper (http://is.gd/yodBQx).
Snohomish County Executive John Lovick and Public Works Director Steve Thomsen said Monday night they were not aware of the 1999 report. "A slide of this magnitude is very difficult to predict," Thomsen told The Times. "There was no indication, no indication at all."
Pennington said officials would examine the report, but he said local authorities were vigilant about warning of potential landslide dangers. A less severe slide struck the area in 2006.
"We've done everything we could to protect them. We've mitigated the landslide from 2006," Pennington said at a morning news conference. "We're going to get to the bottom of this."
He said the local homeowners "were very aware of the slide potential."
The threat of potential flash floods or another landslide also loomed over rescuers. On Monday, some crews had to pull back because of concern that a hillside could shift.
Hots said dozens of searchers will continue throughout the day. The dry, sunny weather has turned to rain, which was expected to continue throughout the day.
"It's going to further complicate things, slow things down a bit," Hots said.
Le reported from Seattle.