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The tornado that left two people dead and dozens of homes destroyed in central Illinois Thursday spanned nearly 20 miles and delivered winds of up to 200 mph, the National Weather Service said Friday, classifying it as an EF4 — the second most intense classification on the tornado rating scale.

In central Illinois, residents were carefully sifting through huge piles of debris in the "absolutely devastated" town of Fairdale, the scene of one of two tornadoes late Thursday. Two people were killed there, according to authorities.

One of the victims was identified Friday as Geraldine M. Schultz, 67. Another woman was discovered Friday afternoon, Illinois Gov. Bruce Rauner said Friday, and identified by the county coroner's office as 69-year-old Jacklyn Klosa. The two women lived next door to each other, according to NBC Chicago. The women were friends and Schultz, known as "Geri," would sometimes drive Klosa to medical appointments, according to The Associated Press.

Nearly every structure in the tiny unincorporated town about 80 miles northwest of Chicago was damaged, said Rockland Fire Department Chief Matt Knott. Some homes were leveled "down to the slabs," he said.

"This town is absolutely devastated," Knott said.

The National Weather Service said the destructive tornado, although accompanied by at least two other twisters, was a “single long track tornado.” The half-mile wide tornado, which carried winds between 180 and 200 mph, was classified as an EF4, according the NWS. Mike Bardou, a meteorologist with the National Weather Service, said EF4 tornadoes only hit the Chicago area about twice a decade.

"We’re very blessed that more people were not hurt," considering the "complete destruction of so many homes with people in them," said Rauner. The governor declared DeKalb and Ogle counties disaster areas Friday. The counties will now receive support from the state.

Ogle County Sheriff Brian Van Vickle said 49 homes in the county had been damaged, including about 30 that had been destroyed. The sheriff's own home was among those that had been completely flattened, he said.

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At least 20 people in the community of about 200 residents were taken to the hospital with injuries of various degrees, and six stayed overnight, officials said. One was in serious condition Friday.

Schultz had been in her house, which was "totally destroyed," DeKalb County Coroner Dennis Miller said Friday. The town was not equipped with tornado sirens, he said.

The National Weather Service said Friday that storms damage survey teams “will be deployed to work with emergency management and assess the damage that has occurred.”

Daniel Prothero, who encountered the scene as he was driving through the area, said, "It was horrible."

Power was shut off to Fairdale so search and rescue crews would be safe, said George Gaulrapp, a spokesman for Commonwealth Edison Co., who said, "It looks like a bomb went off."

"It's a tragedy," Gaulrapp said. "We just pray for the families."

Photo Gallery: Survivors Sift Through Tornado Debris

One of the tornadoes destroyed a restaurant and flattened at least four houses in nearby Rochelle, authorities said. About a dozen people who were trapped in the restaurant's basement were believed to have been rescued safely. Any injuries were minor and didn't require ambulances, they said.

Caleb Bryan was driving from his home in Lindenwood to Rochelle when the tornado hit.

"It was a very scary sight, heavy hail beforehand on Route 251 driving to Rochelle," he told NBC News. "As soon as the storm passed, I drove home to make sure it was still there."

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Police told NBC News there was also significant damage in the towns of Kings and Hillcrest. There was no immediate word on injuries there.

More than 900 departures and arrivals were canceled at Chicago's O'Hare International Airport, and more than 950 others were delayed Thursday night.

The tornado was one of several that spun off across Illinois and Iowa on the second day of a monster storm system that peppered a 1,500-mile arc with grapefruit-size hail and winds up to 80 mph from Texas up to the Great Lakes and across to North Carolina.

A separate EF1 tornado hit Summerfield Zoo in Belvidere and killed an emu and a swan, according to the zoo and NWS. Zoo officials said the park sustained $200,000 in damages, but two baby goats were born during the tornado and a swan that survived managed to protect her eggs.

On Friday, the front responsible for the severe weather moved south and east. A funnel cloud was spotted in Charles, Louisiana, on Friday afternoon, and 62 mph winds knocked down trees in Buffalo, New York, according to Weather.com. Maryland and Virginia were at the greatest risk for thunderstorms and possible tornadoes on Friday night, according to the NWS.

NBC News' Emmanuelle Saliba contributed to this report.