Rescue officials said the death toll from a catastrophic mudslide in Washington state is soon expected to climb far higher, as some residents voiced anger that they were prevented from helping in the initial disaster response six days ago.

At least 26 people were known to have perished when a rain-soaked hillside collapsed without warning on Saturday, unleashing a deluge of mud that flattened dozens of homes in a river valley near the rural town of Oso, in Snohomish County, some 89km northeast of Seattle.

Al Jazeera's John Hendren reports from Seattle.