Searchers found five more bodies Sunday in the sludge of a massive landslide in the northwestern state of Washington, bringing the death toll to at least eight from the wall of debris that swept through a small riverside neighbourhood.

Four more bodies were discovered late Sunday, said Snohomish County sheriff's Lt. Rob Palmer said. Earlier in the day, authorities said one body had been found on the debris field. Three people were already confirmed dead on Saturday.

More people remained missing, and authorities said the number was "fluid." Earlier Sunday, they said it was at least 18, but that count came before additional bodies were discovered.

The mudslide that struck Saturday morning also critically injured several people and destroyed about 30 homes.

Snohomish County Fire District 21 Chief Travis Hots said Sunday evening that crews were able to get out to the muddy, tree-strewn area after geologists flew over in a helicopter and determined it was safe enough for emergency responders and technical rescue personnel to search for possible survivors.

"We didn't see or hear any signs of life out there today," he said.

Despite that, Hots said crews were still in a "search and rescue mode. It has not gone to a recovery mode at this time."
 
He said the search would continue until nightfall, when conditions would become too dangerous. Some rescue workers had been mired in mud up to their armpits and had to be dragged to safety on Sunday, authorities said.

At a press conference late Sunday, officials announced they had been given the resources to continue the ground search overnight.

Neighbourhood 'is not there anymore'

The slide of mud, trees and rocks happened about 11 a.m. Saturday. Several people — including an infant — were critically injured and the slide destroyed about 30 homes.​

Before crews could get onto the debris field late Sunday morning, they looked for signs of life in the quicksand-like mud below by helicopter.

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The Oso Community Church displays a sign reading "pray with us for our community" in Oso off of Highway 530 on Sunday, the day after a giant landslide occurred near mile marker 37. (Lindsey Wasson/Seattle Times/AP)

Rescuers' hopes of finding more survivors were buoyed late Saturday when they heard people yelling for help from within the debris field, but they were unable to reach anyone. The mud was so thick and deep that searchers had to turn back.

Rescuers heard nothing when they got closer, and the decision was made to retreat because it was too dangerous, Hots said Sunday.

"We have this huge square-mile mudflow that's basically like quicksand," he said.

The slide wiped through a 2.6-square-kilometre area of what neighbours described as a former fishing village of small homes — some nearly 100 years old. The neighbourhood "is not there anymore," Hots said.

Because of the unstable situation, authorities said it was initially too dangerous to send rescuers on foot into the area Sunday. But Hots said the geologists told them later Sunday they could venture out.

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Raw footage shot Saturday from a Washington State Patrol helicopter shows the area of the mudslide. (SnoCo Sheriff/YouTube)

As the search for the missing continued, authorities said some may have been able to get out on their own. The number unaccounted for could change because some people may have been in cars and on roads when the slide hit just before 11 a.m. Saturday, Hots said.

Officials described the mudslide as "a big wall of mud and debris."

It blocked about 1.6 kilometres of State Route 530 near the town of Oso, about 90 kilometres north of Seattle. It was reported about 18 metres deep in some areas.

Authorities believe the slide was caused by ground made unstable by recent heavy rainfall.

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Barbara Welsh, center, a mudslide victim whose husband is still missing, is comforted by Washington Gov. Jay Inslee, right, following a news conference outside of the Arlington Police Department on Sunday. (Jordan Stead/seattlepi.com/Associated Press)

Washington state Gov. Jay Inslee described the scene as "a square mile of total devastation" after flying over the disaster area Sunday.

He assured families that everything was being done to find their missing loved ones.

"There is a full scale, 100 per cent aggressive rescue going on right now," said Inslee, who proclaimed a state of emergency.

Officials fear debris dam breach

The slide blocked the North Fork of the Stillaguamish River, which prompted an evacuation notice Saturday night because water was rising rapidly behind the debris.

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A fatal mudslide brought debris down onto a small neighbourhood and the Stillaguamish River near Oso, Wash., destroying several homes and stopping the flow of the river. (Genna Martin/The Herald/Associated Press)

Authorities worried about severe downstream flooding if water suddenly broke through the debris.

Snohomish County officials said Sunday that residents could return home during daylight hours, but that they'll likely re-issue the evacuation order Sunday night.​  The water had begun to seep through the blockage Sunday afternoon.

Even though the evacuation had been lifted, Inslee urged residents to remain alert.

Officials with the Snohomish County Emergency Management Department said there were concerns that the water could break downstream, as well as back up and flood areas upstream.

The National Weather Service issued a flash flood watch for Snohomish County through Monday afternoon.

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Neighbors gather at the Oso Fire Department to look for updates about the fatal mudslide that washed over homes east of Oso, Wash., on Saturday. (The Daily Herald/Annie Mulligan/Associated Press) (Annie Mulligan/The Daily Herald/AP)

Shari Ireton, a spokeswoman for the Snohomish County sheriff's office, said Sunday a total of eight people were injured.​

A 6-month-old boy and an 81-year-old man remained in critical condition Sunday morning at Harborview Medical Centre in Seattle.

Hospital spokeswoman Susan Gregg said two men, ages 37 and 58, were in serious condition, while a 25-year-old woman was upgraded to satisfactory condition.

Five of the injured were brought to Cascade Valley Hospital in Arlington, and one has already been treated and released, said hospital spokeswoman Jennifer Egger. She didn't know the condition of the others.

Bruce Blacker, who lives just west of the slide, doesn't know the whereabouts of six neighbours.

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Robin Youngblood, who survived the landslide that destroyed her house, is holding the only item that survived the disaster, a painting of a Cherokee warrior that was knocked from the wall and muddied. "It saved us." she said. (Mark Harrison/Seattle Time/AP)

"It's a very close knit community," Blacker said as he waited at an Arlington roadblock before troopers let him through. There were almost 20 homes in the neighbourhood that was destroyed, he said.

"I'm hoping for the best," Blacker said.

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.

Dane Williams, 30, who lives a few kilometres from the mudslide, spent Saturday night at the 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 who live in the stricken area.

"It makes me want to cry, just looking at them," Williams said Sunday.

'Gone in three seconds'

One eyewitness told the Daily Herald that he was driving on the roadway and had to quickly brake to avoid the mudslide.

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Snohomish County shared these images of the landslide on Facebook Saturday night. A large chunk of earth appears to have fallen away from a hill above the Stillaguamish River near Oso, Wash. (Snohomish County)

"I just saw the darkness coming across the road. Everything was gone in three seconds," Paulo Falcao told the newspaper.

Search-and-rescue help came from around the region, plus the Washington State Patrol and the Army Corps of Engineers. More than 100 rescuers were at the scene.

The National Weather Service issued a flash flood watch for Snohomish County through Sunday afternoon.

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.

Pennington said Saturday's slide happened without warning.

"This slide came out of nowhere," he said.

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A comparison of a Google Earth rendering of the slide area, left, and an aerial photo taken by Andrew Albert, right. (Aerial image by Andrew Albert. Comparison by CBC News)

Map: Approximate slide area

With files from CBC News, Reuters