A rare tornado slammed into downtown Salt Lake City without warning shortly before 1 p.m. yesterday, killing at least one person, injuring scores of others and leaving the city's central business district a paralyzed jumble of uprooted trees, downed power lines and damaged vehicles.

The twister struck the city from the west, inflicting the most destruction around the downtown Delta Center, home of the Utah Jazz basketball team, and then slashing through a nearby residential area near the state capitol. Witnesses described a terrifying few minutes at the height of the storm, when they said the air was filled with rain, hail and swirling debris from buildings hit by the tornado.

"It looked like the city dump was in the sky," said Kim Bramble Valles, 26, who watched the tornado with her children at the home of her parents. "It was pretty freaky."

Diane Samie, a sales representative, said she was waiting to pick up lunch at a drive-through window across from the sports arena when the tornado hit.

"It started raining, got dark. Lightning hit something near us, then we started seeing debris swirling in the air," she said. "There were parts of roofs, paper, plastics flying around and we watched one crane go down half a block away."

Last night, downtown Salt Lake City was closed to all but emergency crews trying to restore electricity, remove downed trees and shovel debris from streets. Workers in cherry pickers were removing broken plate glass windows from the Delta Center as other maintenance workers inspected and repaired damage at the Wyndham Hotel.

"Power lines were knocked down, trees came down on cars," said Alicia McGregor, public information officer with Utah Emergency Management. "A lot of trees are blocking major roads."

The tornado struck in the most densely populated area of the city, home not only to the Delta Center, but also to numerous high-rise office buildings, hotels and other structures.

Mayor Deedee Corradini said she hoped to have the area open by 7 a.m. Thursday. The mayor said 63 to 69 people were injured and transported to hospitals, a dozen in serious or critical condition and one 43-year-old woman in very critical condition. Corradini said there had been only one fatality.

"This in many ways was a miracle," Corradini said. "It could have been so much worse."

"The movement and the magnitude of the funnel was just extraordinary," said James Gomez, spokesman for LDS Hospital in the Avenues neighborhood, the hardest hit residential area. "I kept telling myself, `We are not supposed to have these things in Utah. We have mountains.' "

Gov. Mike Leavitt (R) viewed the scene from a helicopter and announced that he will issue a state disaster declaration.

"It was one of the most awesome things I've ever seen," Leavitt said. "Homes in the Avenues had their roofs torn off and the damage to the Delta Center [seen] from above is incredible." Several witnesses said the roof of the Delta Center was blown off.

But by far the most significant damage occurred at Salt Lake City's Outdoor Expo, a temporary tent structure set up for a retailers' show. Tents there were flattened, but Corradini said the show, which brings 20,000 people to the city, would only be postponed a day and start on Friday.

Authorities said Allen Crandy, 38, of Las Vegas was killed when he was struck in the head by flying debris, the Associated Press reported. Crandy worked for Renaissance Management and was an exhibitor at one of the outdoor retailer tents.

Chase Nash, a security guard at the show, said that as winds tore through the circus-like tent, "people were diving under the tables and pretty much panicking. I saw the roof fall off and then the metal beams supporting the structure started flying everywhere."

"It was very quick and very sudden," he added. "We only had about 15 seconds from when we first saw the tornado hit the Delta Center until it hit us."

Nash, who was struck in the back by one of the metal beams, said he found one seriously injured person in the collapsed structure. "We didn't dare move him," he said. "He obviously had neck and back injuries. So we just stayed with him a few minutes, but emergency personnel arrived very quickly and took over for us."

"Everything it hit it completely destroyed," said Verdi White, deputy director of Utah Emergency Management.

Except for where it piled things up. In the Avenues neighborhood, city police Officer Nick DeLand said, "A lady now has two garages in her back yard, and she started out with none."

Corradini said 121 houses had been damaged, and 34 of them are uninhabitable. A shelter was opened for homeless Avenues residents, and elsewhere people scrambled to find hotel rooms. Several hundred guests of the downtown Wyndham Hotel were displaced when the hotel closed after its windows were blown out.

Jim Campbell, deputy director of the National Weather Service western regional office in Salt Lake City, said his office issued a severe thunderstorm warning at 12:48 p.m., about five minutes before the twister touched down. Campbell said he classified the tornado as F-2, on a scale in which F-1 is the weakest and F-5 the strongest. He said the tornado was on the ground for about 1 1/2 miles and stretched 300 yards wide in some places as it moved at about 100 mph.

In Washington, President Clinton issued a statement promising federal help for recovery from the tornado. "The burden of recovery will be heavy, but it is a burden that the people of Salt Lake City need not carry alone," he said. Corradini said Federal Emergency Management Agency teams were on the way last night.

Valles, who was at her parents' home, said that just before the tornado struck, someone in the house remarked, " `Oh, good, it's going to cool the house off.' The next thing you know, it was rain and hail. I ran out to my car to close the windows and it was a twister. I don't think there was any warning."

At the height of the storm, Valles said, she saw "a big red burst" at the Delta Center. Ray Bramble, 61, her father, said that it was at that moment that his 8-year-old grandson informed him that the Delta Center "just blew up."

"At first I thought it was a hailstorm, then we could see the twirling debris, huge chunks of Styrofoam from the Delta Center," Bramble said. "The whole neighborhood is full of these huge four-by-four-by-four hunks of Styrofoam."

Bramble, a retired psychotherapist, said of the experience: "We don't have a reference for tornadoes [in Utah] and we're kind of smug. We always think the mountains are going to protect us from everything. It got us this time. It was, at best, interesting."

Walsh reported from Washington, Kenworthy from Salt Lake City. Staff writer Ceci Connolly, research editor Margot Williams and staff researcher Ben White in Washington and special correspondent Dave Hancock in Salt Lake City contributed to this report.