Jonathan J. Cooper?and Lisa Baumann

DARRINGTON, WASH.: Many of the dogs essential in the search for victims of the deadly mudslide that buried a mountainside community will take a two-day break, rescue crews said Sunday, as the official death toll rose and more bodies were recovered.

The dogs can lose their sensing ability if overworked in the cold and rain.

“The conditions on the slide field are difficult, so this is just a time to take care of the dogs,” said Kris Rietmann, a spokeswoman for the team working on the eastern portion of the slide, which hit March 22 about 55 miles northeast of Seattle and is one of the deadliest in U.S. history.

Dogs from the Federal Emergency Management Agency that arrived more recently will continue working.

On Sunday evening, the number of people who have been confirmed dead increased from 18 to 21, said Jason Biermann, program manager at the Snohomish County Department of Emergency Management.

Fifteen of the victims have been identified by the Snohomish County medical examiner, and six have yet to be identified, Biermann said.

Another four bodies were found in the debris field on Sunday, but they won’t be added to the official count until the medical examiner receives the bodies. Biermann said 30 people remain missing.

Authorities have said the task of finding and identifying victims from the debris field has been extremely challenging, and not all may ultimately be recovered.

Crews have completed a makeshift road that will link one side of the debris field to the other, significantly aiding the recovery operation.

They have also been working to clear mud and debris from the highway, leaving piles of gooey muck, splintered wood and housing insulation on the sides of the road.

Searchers have had to contend with treacherous conditions, including septic tanks, gasoline and propane containers. When rescuers and dogs leave the site, they are hosed off by hazardous materials crews.

The slide dammed up the North Fork of the Stillaguamish River, causing water to pool up on the east side. The river cut a new channel through the mud, but the rain has raised the water level nearly a foot, Rietmann said.

In at least one place, the water level got so high that it covered areas that have already been searched, said Tim Pierce, leader of Washington Task Force 1, a search-and-rescue team.

“At this point, there’s no point in searching [that area] again until the water drops back down,” he said.

Rescuers should get some relief soon. Conditions were improving Sunday, and mainly dry weather is forecast today through Wednesday in western Washington.

The size of the debris field is also smaller than initially thought, officials said Sunday. Geologists have determined it is about 300 acres — just under half the size of an earlier projection of 1 square mile.