One worker was killed and nine were injured yesterday after a powerful gust of wind slammed into a 20-foot-tall cinderblock wall under construction in Fairfax County, causing the wall to tumble down onto the workers perched on scaffolding behind it.

Witnesses said the wall vibrated, and then collapsed, as frightened workers tried to scramble down to the ground. "It was just, I mean, pwoof!" said Albert Crites, a mason working on another section of the wall. The wind "just twisted the scaffolding, and then the wall just started going with it."

The first of 55 rescue workers to reach the muddy construction site next to Sully Plaza in Chantilly were met with "total chaos," said Sgt. Greg Bunch, with Fairfax County's Rescue Squad 21. "They were hollering out in pain."

Co-workers and friends picked through the rubble, trying to help those who were covered with cinderblocks and pieces of scaffolding, Bunch said. About 40 minutes passed before the last worker was extricated and sent to one of two hospitals, he said.

Crites, 45, who lives in West Virginia and works in Fairfax, said he ran to one of the most seriously injured workers, whose face was buried in the mud. "I put my fingers under his face and tried to dig a ditch under his head so he could breathe," he said.

The dead worker was identified as William Dixon, 34, of Winchester. Dixon was taken to Fair Oaks Hospital, where he died of massive head injuries, a hospital spokeswoman said. Another man was admitted there in serious condition, two were listed as fair and a fifth was treated and released, she said.

At Fairfax Hospital, a 31-year-old man was reported in critical condition. Two men were in serious condition, one was in fair condition and a fifth was treated and released, authorities said.

Despite the death and injuries, the incident proved less serious than early reports suggested. Responding to warnings that as many as 20 workers were buried, both hospitals prepared to shift into "disaster mode" -- their highest state of readiness.

"We were gearing up," said Jane Welch, Fairfax Hospital spokeswoman. Surgeons, social workers, pharmacists, radiologists and surgical residents were standing by for the first wave of injured workers into the trauma center, she said.

The number and severity of injuries were less than feared, said hospital officials, who said the injuries included broken bones, fractured ribs and chest and abdominal trauma.

As rescue workers were digging people out of the rubble, investigators were trying to determine whether proper procedures were followed at the site of what will be a Service Merchandise store along Route 50 near Metrotech Drive.

Brian Smith, deputy director of the county's Division of Inspection Services, said that a preliminary look did not reveal any building code violations. However, he said it was obvious to him that the wall had not been adequately secured.

"The wall in essence is like a big sail," Smith said. "It was simply the wind . . . . I think by virtue of definition, bracing was inadequate."

Smith said the wind gust was estimated at 20 to 40 miles an hour. Dulles Airport recorded a peak wind gust of 41 mph about the time the wall came tumbling down.

Wayne Hobbs, president of Keystone Builders Inc., the general contractor for the project, said proper procedures were followed and that the gust was sudden. The wind "exploded -- it really did," Hobbs said. "It just came in on them all of a sudden."

Employees of the Occupational Safety and Health Program, part of the Virginia Department of Labor and Industry in Richmond, were at the site looking for any safety violations, said spokeswoman Lilia Williams. Their investigation could take weeks, she said.

Fairfax Hospital spokeswoman Welch said the names of the five victims treated there could not be released because some relatives had not yet been notified. Fair Oaks Hospital said Jose Delcid, 25, was in serious condition; both Michael Marshall, 21, and Jose Alcontora were listed as fair; and Patrick Reed, 34, was treated and released.