Hopes are diminishing for finding survivors of a U.S. mudslide that has already killed eight people, with more reported missing.

Rescue workers continued their search Monday of a large quicksand-like debris pile in the northwestern state of Washington. It is a mix of mud and trees covering 2.6 square kilometers and nearly five meters high in some places.

One survivor was caught up in the wall of mud, trees and rocks as it cascaded through a rural community north of Seattle on Saturday morning.

"There was literally a 20-foot-wall of mud racing across the valley.... we were tumbled inside (our house) and had mud in our eyes and nose and mouth. I am really grateful I am alive."

A fire department spokesman said late Sunday that rescuers did not hear any signs of life in the debris pile. Eighteen people had been reported missing, but that was before rescue workers found five bodies Sunday, pushing the death toll to eight.

The mudslide destroyed as many as 30 houses in its path and injured eight people.

Officials blamed the mudslide on groundwater saturation after recent heavy rainfalls.

One motorist described seeing the mudslide.

"I was the third car behind a truck with a boat. I saw the darkness washing everything off the road. I am not sure that truck made it through."