As many as 108 people were listed as missing two days after a mudslide hit dozens of homes and killed at least 14 people in Washington state.

Authorities said many individuals still unaccounted for are ultimately expected to turn up safe.

Still, emergency management officials expressed doubt that anyone else would be found alive from the muck and debris.

Concern also lingered about flooding from water backing up behind a crude dam of mud and rubble dumped into a river by Saturday's slide.

"The situation is very grim," said Travis Hots, Snohomish County District 21 Fire Chief.

"We're still holding out hope that we're going to be able to find people that may still be alive.

"But keep in mind we haven't found anybody alive on this pile since Saturday in the initial stages of our operation."

The landslide was triggered after a rain-soaked hillside along State Route 530 near Oso, Washington, gave way, washing away at least six homes in an area about 90km northeast of Seattle.

In all, at least 49 homes were believed to have sustained some damage from the slide, said John Pennington, director of the Snohomish County Department of Emergency Management.

That figure was derived from the total number of land parcels – at least 112 - swept by the cascade of mud and known to have homes or other structures built on them.

The search for victims resumed today after treacherous quicksand forced rescue workers to suspend their efforts yesterday.

Some workers, mired in mud up to their armpits, had to be dragged to safety.

A spokesman for the Snohomish County Sheriff's Office said  14 bodies had been found in the 2.6 square km disaster zone of tangled debris, rocks, trees and mud.

Another eight people were injured in the landslide.

"I have a sense that we're going to have some hard news here," Washington Governor Jay Inslee said after flying over the affected area.

A state of emergency has been declared in Snohomish County.