Soupy 'quicksand' has kept rescuers from searching entire area.
Searchers don't expect to find any more survivors from Saturday's mild-wide slide, which killed at least eight people.
Authorities are looking into 108 reports of missing persons following the Washington mudslide. No one has been found alive since Saturday.
"We're still in rescue mode at this time, but the situation is very grim," said Chief Travis Hots of Snohomish County Fire District 21. "We have not found anybody still alive on this pile since Saturday."
Authorities assembled Monday's list of 108 missing and unaccounted-for people over the past two days, and it includes some vague information, said John Pennington, Snohomish County emergency management director.
"In some cases, that list is very detailed. It's 'John, who has brown hair, blue eyes and lived in this particular neighborhood.' "Pennington said. "In a lot of cases, it's a name like Frank, 'I met him once. I think he lived over there.' "
Among the missing: residents, construction workers and people just driving by.
County officials are encouraging people who have reported someone missing on social media or a website, including people who are safe, to call a Snohomish County hot line so officials can update their database. They expect the number of people missing to decrease but have been worried that many people were at home when the slide wiped out about 30 houses around 11 a.m. PT Saturday.
Additional state and federal resources to help the more than 100 emergency responders already at the scene are being brought in to aid in the recovery effort, including search dogs and technical rescue experts. The Washington State Department of Transportation is bringing in heavy equipment to clear some of the mud.
Search and rescue teams but had to pull back Monday because of concern about the hillside moving.
Rescuers' spirits had been raised late Saturday when they heard voices calling for help from the flotsam of trees, dirt and wreckage. Dangerous conditions forced them to turn back in the darkness, but they resumed their work at first light Sunday.
"We didn't see or hear any signs of life out there," Hots said Sunday. "It's very disappointing to all emergency responders on scene." Sunrise on Monday was 6:59 a.m. PT; sunset will be at 7:27 p.m.
Among the missing are the wife and granddaughter of Oso firefighter Seth Jefferds. He and his stepdaughter had gone to run errands in Oso when the earth started sliding above Jefferds' home. Christina Jefferds, 45, was babysitting 4-month-old Sanoah Huestis at the house.
Barbara Welsh, who came to a news briefing Monday, said she hasn't seen her husband, William Welsh, since Saturday when he went to help someone in Oso with a water tank.
Four bodies were discovered late Sunday, Sheriff's Lt. Rob Palmer of Snohomish County said. Earlier in the day, one body had been found on the debris field. Three people were confirmed dead Saturday.
The body of Linda McPherson, 69, whose family had lived on their farm outside Oso for five generations, was among those found Sunday, according to a family friend. Her husband, Gary "Mac" McPherson, was one of eight people injured in the mudslide; his condition was not immediately available.
A 6-month-old boy and an 81-year-old man were in critical condition Sunday at a Seattle hospital. Hospital spokeswoman Susan Gregg of Harborview Medical Center said two men, ages 37 and 58, were in serious condition while a 25-year-old woman was upgraded to satisfactory condition. Other hospitals reported a woman in satisfactory condition and a 68-year-old man in stable condition.
As relatives went to the McPherson farm Sunday in search of Linda McPherson and anything that could be salvaged, her grandnephew heard the family's Labrador retriever whining. Buddy apparently had ridden the slide for about 100 yards and then
The soupy, tree-strewn area has mud that is 15 feet deep in places. Crews were able to get there Sunday after geologists flew over in a helicopter and determined it was safe enough for emergency responders to search for possible survivors, Hots said.
Rescuers have not searched the entire debris field, only drier areas believed safe.
"We have this huge square-mile mudflow that's basically like quicksand," Hots said.
The slide wiped through what neighbors described as a former fishing village of small homes, some nearly 100 years old.
The slide blocked about a mile of Washington 530 near the town of Oso, which has fewer than 200 residents. It is about 55 miles northeast of Seattle.
Mud-splattered pictures in a home effected by the March 23, 2014, fatal mudslide near Oso, Wash.(Photo: Genna Martin, AP)
The cause of the mudslide was most likely unstable ground after recent heavy rainfall, authorities said.
In the past 45 days, the area has had double its normal rainfall, at least 15 inches higher than normal, according to the National Weather Service. More rain is forecast Tuesday.
Frequent heavy rainfall and geography make the area, carved by the Stillaguamish River and glaciers, prone to landslides. The area had a similar slide in 2006, and erosion from the rain had caused the base of the previous slide to weaken.
"This is a completely unforeseen slide," Pennington said Monday. "It happened in 2006, ... but this came out of nowhere. They had no warning."
The 1,500-foot wide slide blocked the North Fork of the Stillaguamish River and water pooling behind the debris flooded seven homes up to their eaves, Pennington said.
The water began to seep through the blockage Sunday afternoon, alleviating some concerns, and was starting to route around the debris.
"The river started cutting a new channel through," said Steve Thompson, Snohomish County public works director, using the stream bed it was in before the 2006 landslide. "That's good news. It's doing what we expected it to do."
Relieving the pressure behind the slide is important not only to prevent more damage but also so rescuers can get into areas now under water and mud, he said. Five bridges are downstream from the slide, and workers are monitoring to make sure that logs and other debris don't endanger them.
The weather service continued its flash flood watch for Snohomish County through Monday afternoon.
Bruce Blacker, who lives just west of the slide, doesn't know the whereabouts of six of his neighbors.
"It's a very close-knit community," Blacker said as he waited at an Arlington roadblock before troopers let him through.
Dane Williams, 30, who lives a few miles from the mudslide, spent Saturday night at a Red Cross shelter in Arlington.
He said he saw a few "pretty distraught" people at the shelter who didn't know the fate of loved ones.
"It makes me want to cry," Williams said.
Linda Byrnes, a former Arlington council member, checked on friends and others in the community Monday.
"What they're doing is hanging out with each other, holding each other up," she said. "You can't live here without knowing someone who is unaccounted for."
Contributing: Zahid Arab and Chris Daniels, KING-TV, Seattle-Tacoma, Wash; The Associated Press