(Corrects spelling of Oso in last line)
By Eric M. Johnson
OSO, Wash., March 31 (Reuters) - Recovery teams struggling through thick mud up to their armpits and heavy downpours at the site of a devastating landslide in Washington state are facing yet another challenge - an unseen and potentially dangerous stew of toxic contaminants.
Sewage, propane, household solvents and other chemicals lie beneath the surface of the gray mud and rubble that engulfed hundreds of acres of a rural community on March 22 and left dozens of people dead or missing, authorities said.
The official death toll rose to 24 on Monday - up from 21 a day earlier, nine days after a rain-soaked hillside collapsed above the north fork of the Stillaguamish River, northeast of Seattle. The dead included a 4-month-old infant and two older children, ages 5 and 6.
Authorities said the number of people still listed as missing had been cut to 22 from 30. It was not immediately clear if that number was lowered through the identification of bodies. Of the 24 dead, 18 have been identified by medical examiners.
Meanwhile, managers of the recovery operation were taking special measures to protect the hundreds of workers on the scene from chemical exposure and to prevent toxic sludge from being carried offsite.
"We're worried about dysentery. We're worried about tetanus. We're worried about contamination," local fire Lieutenant Richard Burke, a spokesman for the operation, told reporters visiting the disaster site. "The last thing we want to do is take any of these contaminants out of here and take them into town, back to our families."
The torrent of mud released by the slide roared over both stream banks of the Stillaguamish river and across state Highway 530, flattening dozens of homes on the outskirts of the town of Oso in the foothills of the Cascade Mountains.
The death toll in the disaster has been somewhat of a moving target in recent days as county officials have reported locating a number of bodies without adding them to their fatality toll.
Search crews, with the help of dogs, have been regularly finding and retrieving more remains, at least four to six times a day on the eastern half of the massive debris pile, recovery team supervisor Steve Harris told a news conference.
But authorities have said the process of accounting for the number of dead has been complicated by the fact that the bodies are not always found intact.
Harris said the mudslide struck with such force that whole cars were "compacted down to about the size of a refrigerator, just smashed to the point where you can hardly tell it was a vehicle."
No one has been pulled out alive and no signs of life have been detected in the disaster zone since the day the slide hit, when eight people were injured but survived.
Officials have conceded it may be impossible to account for everyone lost in the disaster, and that some victims might end up being permanently entombed under the giant mound of muck and debris covering about a half square mile (1.3 square km).
Asked how much longer the search efforts would continue to be formally treated as a rescue operation, Harris said, "I can't answer how long this is going to go on. There's a lot of work to be done yet."
Jaime Smith, a spokeswoman for Governor Jay Inslee, said that decision would ultimately be made by the joint incident command, consisting of the on-site leaders of the various local, state and federal agencies involved in the search.
Scores of recovery workers, including National Guard troops just back from Afghanistan, picked through the swampy, rubble-strewn mud on Monday under bright, sunny skies that provided a welcome respite from heavy rains of last week.
Weather forecasts for the week ahead showed a continued drying trend, "which will help crews and reduce the risk of flooding and additional slides," the county said in a statement.
The break in the weather means less logistical work, such as pumping out water, and more actual searching, Burke said.
But about a third of the site remained buried beneath 60 to 80 feet (18 to 24 meters) of mud, twisted tree trunks and wreckage, making it too unstable to safely enter, he told reporters.
Like most workers at the site, Burke's boots were sealed to his trousers with duct tape, a precaution to keep toxic sludge out of his clothing. National Guard troops also set up a decontamination station where workers scrubbed themselves with soap and hot water before leaving the site.
"This is going to be a hazardous materials site for many years while we try to get this cleaned up," Burke said.
Governor Inslee, who toured the disaster zone by helicopter on Sunday, asked President Barack Obama on Monday for a major disaster declaration that would make federal programs available to assist people, households and businesses affected by the slide.
The request followed the approval of a federal emergency declaration last week that paved the way for the U.S. government to send in its own disaster team and specialized personnel.
In a bid to boost gloomy spirits in the community, members of two of Seattle's professional sports teams, the Seahawks of the National Football League and the Sounders Major League Soccer team, planned to visit the area later on Monday.
Dennis Smith, chief executive of the county's United Way chapter, said his nonprofit charity organization had raised an unprecedented $1.2 million with a special campaign benefiting victims and survivors of the Oso landslide. (Additional reporting by Jonathan Kaminsky in Oso, Bill Rigby in Arlington, Washington, and Steve Gorman and Dan Whitcomb in Los Angeles; Writing by Steve Gorman; Editing by Andrew Heavens, Dan Grebler and Lisa Shumaker)