Search efforts at the mudslide in the US state ofWashington were slowed down by unstable mud that at times forcedrescuers to retreat Tuesday, dpa reported."It's a kind of a slurry where it's not solid enough to support aperson's body walking on it but too solid to take a boat," JayInslee, governor of Washington state, told broadcaster CNN.But he said there were some "very aggressive searchers" who werewilling to take some risks, and others who were using hovercraft tosearch the debris area.The governor also received a call from the White House Tuesday todiscuss the mudslide and the rescue efforts.About 300 rescuers are involved in the search, but "all the search and rescue teams in the world are not enough," Inslee added.The unconfirmed list of missing in the mudslide wreckage stood at 176as rescuers continued to search for signs of life amid massivedebris.Chances of finding victims alive trapped in the mudslide are dimming.