OSO, Wash. — First there was a “whoosh.” Elaine Young said she thought it might be a chimney fire, a rush of air that lasted about 45 seconds. But when she stepped outside there was ominous silence. Something felt very, very wrong.

And then she saw it. Behind the house, a suffocating wall of heavy mud had crashed through the neighborhood.

Dark and sticky, the mile-long flow Saturday heaved houses off their foundations, toppled trees and left a gaping cavity on what had been a tree-covered hillside. In the frantic rescue, searchers spotted mud-covered survivors by the whites of their waving palms.

At least 14 people are confirmed dead, dozens more are thought to be unaccounted for or missing, and about 30 homes are destroyed.