As thick white ash drifted east into Idaho, clogging streets and closing down cities, Air Force helicopters began combing the charred forest below Mount St. Helens, searching for survivors of Sunday morning's massive volcanic eruption.

Five bodies have been spotted at the volcano, the deaths apparently caused by intense heat or the force of the eruption. Twenty-nine other people, judging by telephone calls from frantic friends and relatives, were in the Mount St. Helens area at the time of the explosion and have not been accounted for.

The missing include loggers, two U.S. Geological Survey employes, a National Geographic magazine photographer and campers -- some of whom may have ignored official warnings about entering the restricted area around the base of Mount St. Helens.

A family of four was rescued by helicopter early this afternoon. There was no immediate report on their condition. In order to bring the family aboard, officials said, members of the rescue team had to stay behind. Along the Toutle River, which turned overnight into a violent torrent of mud, five more stranded people were spotted by helicopters early this afternoon, but there was not enough visibility for the rescue crews to land near them.

Late this afternoon, according to U.S. Forest Service spokesman Jim Unterwegner, an enormous mass of what appeared to be volcanic debris and mud was sighted from an airplane north of Mount St. Helens. The flow looked to be 200 feet deep and three-quarters of a mile wide.

It appeared, Unterwegner said, that the flow had backed up water in the mud-filled Spirit Lake, threatening new flooding and forcing evacuation of residents of several small communities below the mountain, which was described as "still perking."

About 1,000 people were evacuated following the Sunday morning eruption, but some of them have returned to their homes since then.

The Sunday morning blast, the most violent since Mount St. Helens began erupting March 27, literally blew the top off the once-conical volcano. A billowing gray column shot 60,000 feet in the air, and pyroclastic flows -- intensely hot cascades of melted glass formed from silicon-bearing rocks mixed with ashes and gases -- boiled over the lip of the mountain.

Dwight R. Crandell, a geologist with the U.S. Geological Survey, said that fragments of magma, the molten rock that has been simmering underground, have been found in the pyroclastics flow. But he said there has been no sign of the smooth, viscous magma flow that scientists call lava.

"We think that most of the damage was caused by a horizontal blast, a lateral blast of material that just cleared off the ridges," said Crandell. Although there was no way to measure the velocity of the explosion, he said, it was "obviously of hurricane force because trees were just snapped off at ground level, uprooted, five and six miles from the volcano."

There is no way to tell what the volcano might do now, said the Denver-based geophysicist, Joe Rosenbaum: "You could give me 12 possibilities, and I wouldn't pick one." Seven minutes before the eruption, scientists recorded an earthquake measuring about 5.0 on the Richter scale. That earthquake may have been the catalyst that set off this eruption, Rosenbaum said, but even that is speculative.

Crandell, however, believes that some ash eruption may continue "for a period of years." Asked what that might mean for the dust-smothered communities east of Mount St. Helens, he said, "I would expect that they will have continuing and intermittent clean-up problems . . . cleaning grates, ash falling on roofs, ash contaminating everything.

Dot Elmire, owner of the general store in the nearby town of Cougar, said her daughter looked up at the sky and could think of nothing except pictures of the wrath of God. "We looked up," Elmire said, "and it was just phenomenal -- this great huge black boiling column of ash and steam and smoke. It was just unbelievable. There was lightining in it. It came right over us -- we could look right up into it. Everything got dark. I looked up then, and I thought, Oh, good Lord!'"

The blast spewed volcanic ash over the eastern Washington cities of Yakima, Spokane and Pullman, plunging streets into darkness on a bright Sunday afternoon. In Spokane, were the wind whipped thick white dust through streets, officials declared a state of emergency. Schools were closed, and the only businesses allowed open were hospitals, pharmacies and a few doctors' offices. Police wore respiratory masks.

The governors of Montana and Idaho also declared emergencies because of the ash fallout.

The health effects of the ash are still uncertain. But while state laboratories run chemical tests on its composition, health officials are urging people to leave home only when necessary, and then with a face mask. "To my knowledge, there has been no increase so far in the number of respiratory illnesses in the community,' said Dr. M. Marashi, a pediatrician who serves as Spokane County health officer.

Marashi, whose home had been blanketed in volcanic dust, said he had just made a slow, careful drive back from two Spokane hospitals. In one emergency room, Marsahi said, the hospital was handing out free respiratory masks.

At Pullman's Washington State University -- which was otherwise closed for the day -- researchers from the college of agriculture said there was no evidence yet of major damage to the state's wheat crop. They said, however, that small seedlings may be injured or killed by the settling ash.

To residents of the ash-smothered communities east of Mount St. Helens, the university scientist offered this advice: Don't try to wash it off your lawn or it will congeal into a gummy mess. Don't exercise horses or dogs. Don't try to drive your car without an air filter -- when the filter clogs, which it will, replace it or try to blow the dust out from inside. And use detergent to wash your clothes; soap will combine with the volcanic ash and jam your washing machine.

In Plummer, Idaho, 300 miles east of the volcano, the owners of the town's variety store said walking outside was like stepping through ankle-deep dry morter. "It's kind of heavy," said James Allison, "and if just a little moisture touches it, it gets like a paste. . . . You can't move it. . . . On your yard, or grass or anything like that, it just don't move. It just seals over.

"It's kind of like a ghosttown," added his wife, France. "You know that business of Pompeii centuries ago -- and you keep thinking, how could that have happened . . ."