Rescue crews in Snohomish County said Sunday that many of the dogs that have been essential in the search for mudslide victims will take a two-day break.

Days of sniffing through cold, soupy mud and nearly nonstop rain have taken their toll on the animals, and officials say dogs can lose their sensing ability if they work too long.

Crews are still working to recover more victims from the soggy pile of mud that buried part of the small mountainside community of Oso in Washington state more than a week ago.

"The conditions on the slide field are difficult, so this is just a time to take care of the dogs," said Kris Rietmann, lead spokeswoman for the team working on the eastern portion of the slide.

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A search dog roams and sniffs through the debris field caused by a massive, deadly mudslide in Snohomish County. Besides the more than two dozen bodies already found, many more people could be buried in the debris pile left from the mudslide one week ago. (Marcus Yam/The Seattle Times/AP)

Dogs from the Federal Emergency Management Agency, more recent arrivals on the scene, will continue working, said Heidi Amrine, another spokeswoman for the operation.

Engineers were watching for any material sloughing off the landslide area, making sure that a weekend of torrential rainfall doesn't displace more land.

Searchers have had to contend with treacherous conditions, including septic tanks, gasoline and propane containers.

When rescuers and search dogs leave, they're hosed off by hazardous materials crews stationed at the edges of the debris field.

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Shayne Barco said that days of combing through what he called "a blender of debris" has exhausted Stratus. He said the 3-year-old German shepherd has found bodies and body parts, but gets frustrated when they don't bring anybody out alive. (Elaine Thompson/Associated Press)

Authorities have said they have recovered more than two dozen bodies, but they won't be added to the official tally, which stood at 18 on Sunday, until formal identifications are made.

Underscoring the difficulty of identifying those killed in one of the deadliest landslides in U.S. history, officials said the search dogs are not always discovering complete remains.