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MIAMI, Okla. -- An SUV carrying eight mushroom farm workers veered off a snowy highway bridge Thursday and launched itself off an angled, plowed snowdrift and over the guardrail before plummeting more than 80 feet into a shallow icy river below.

Three of the workers were killed and the others were injured after their red Chevrolet Avalanche careened off the Interstate 44 bridge and into the Spring River.

"This is a fall of 80 feet or better . . . that alone is a very dangerous type of crash. This is a very traumatic crash," Oklahoma Highway Patrol Lt. George Brown said. He said all eight were in their 20s.

"The ground temperature was 11 degrees below zero, so it would take only a second to become hypothermic in this water and ice," Brown said.

Two of the victims died when the truck hit the shallow river, and the six others climbed on top of the vehicle, a state trooper who spoke on condition of anonymity because he wasn't authorized to speak to reporters told The Associated Press. He said one of the six, later identified as Douglas Monzon, fell into the river while reaching for a blanket that rescue crews had thrown him, and that crews reached Monzon about an hour later in the river.

Monzon was taken to The Freeman Health Center across the state border in Joplin, Mo., where he was declared dead of his injuries shortly after noon.

Authorities have not released the names of the others killed.

The accident occurred about 6:30 a.m., less than nine hours after officials reopened one of the highway's two westbound lanes. The highway was made impassable Tuesday night by the snowstorm that barreled through Oklahoma and much of the nation, and hundreds of stranded drivers had to be taken to safety.

The trooper who spoke on condition of anonymity said there was no indication that the truck was speeding or being driven in an unsafe manner.

Ottawa County Sheriff Terry Durborow said the truck's driver simply "went airborne."

"I don't know if she lost control of her vehicle or not. She just jumped the guard rail off that bridge," Durborow said.

"It's probably the worst conditions I've seen, and I've lived here all my life," Durborow said.

All of the workers were from the Carthage, Mo., area, about 25 miles east of the accident site, said Scott Engelbrecht, who runs a mushroom farm in Miami where the eight worked. The company, Engelbrecht Farms, was shuttered Wednesday because of the weather and reopened Thursday. Workers heard the news about their colleagues shortly after 9 a.m., he said.

"It's a devastating event and it's tough to know how to deal with it," Engelbrecht said.

Interstate 44 -- also known as the Will Rogers Turnpike -- was shut down when more than 20 inches of snow, sleet and ice fell during a blizzard that stretched from the Southwest to New England. Road crews reopened one lane in both directions Wednesday, but highway officials urged caution as temperatures at 10 below and colder kept roads frozen.

"If people look at the conditions they're driving in, slow down and pay attention and realize they're driving in very hazardous conditions, they're going to make it," said Jack Damrill, a spokesman for the Oklahoma Turnpike Authority.

The plowed snow banks on the bridge formed an almost perfect 45-degree angle. However, Damrill downplayed any suggestion that the road should not have been reopened.

"Yes, there's snow on the sides," he said. "We clear lanes of travel first. There's nowhere for that snow to go. We push everything to the side first to get the lanes open."

Oklahoma began preparing for the snowstorm last week by stockpiling solvents and salts to treat roads, but the size of the blizzard seemed to overwhelm the response. For a time Tuesday and Wednesday, the National Guard and state troopers had to pluck stranded motorists from roadways.

"First, it's only 6 degrees up there with no sunshine. It snowed 20-something inches up there," Damrill said. "This is very unusual to have these kinds of blizzard conditions. Our material doesn't work when it's that cold."

Television footage showed the large vehicle resting upright and partially submerged in the Spring River. A rescuer said the water there was only waist-deep, but Brown said hypothermia would have quickly set in.

Motorists who witnessed the accident said they peered over the side of the bridge and spotted six people outside the truck in the icy water and two others inside the vehicle, Brown said.

"The rescue teams got a small boat, hoisted it down in the water and started the recovery," Brown said.

Grady Weston, the assistant chief of the Newton County (Mo.) Rescue and Recovery squad, said the SUV had broken through ice and was half-submerged when his crews arrived. "Three of us waded out into the river . . . and helped get the last three or four out," Weston said.

Three survivors were at the St. John's Regional Medical Center in Joplin, according to David Morris, the hospital's director of marketing. The Freeman Health Center at Joplin received also received three people, including Monzon. Freeman spokeswoman Christen Stark said one of the other two, Julio Garcia, was in fair condition, but she declined to say how the third was faring.

Brown said all remaining survivors were in serious but stable condition recovering from hypothermia, and that they were expected to survive.

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Murphy reported from Oklahoma City. Associated Press writer Justin Juozapavicius in Tulsa contributed to this report.