ATHENS, Ala. (AP) — Powerful storms stretching from the Gulf Coast to the Great Lakes wrecked two small Indiana towns, killed at least three people and bred anxiety across a wide swath of the country in the second deadly tornado outbreak this week.

Authorities reported the three deaths in southern Indiana, where Marysville was leveled and nearby Henryville also suffered extreme damage. Each is home to about 2,000 people.

"Marysville is completely gone," said Clark County Sheriff's Department Maj. Chuck Adams.

Aerial footage from a TV news helicopter flying over Henryville showed numerous wrecked houses, some with their roofs torn off and many surrounded by debris. The video shot by WLKY in Louisville, Ky., also shows tractor-trailers tossed on their side at a truck stop.

An Associated Press photographer in Henryville said the high school was destroyed and the second floor had been ripped off the middle school next door. Firefighters were searching through the ground floor of the middle school for possible victims.

The rural town about 45 miles north of Louisville is the home of Indiana's oldest state forest and the birthplace of Kentucky Fried Chicken Founder Col. Harlan Sanders.

The threat of tornadoes was expected to last until late Friday for parts of Kentucky, Tennessee, Indiana and Ohio. Forecasters at the National Weather Service's Storm Prediction Center in Oklahoma said the massive band of storms was putting 10 million people in several states at high risk of severe weather.

"Maybe five times a year we issue what is kind of the highest risk level for us at the Storm Prediction Center," forecaster Corey Mead said. "This is one of those days."

Cincinnati-Northern Kentucky International Airport was closed briefly because of debris on the runways. By late afternoon, one of three runways had reopened.

The outbreak was also causing problems in states to south, including Alabama and Tennessee where dozens of houses were damaged. It comes two days after an earlier round of storms killed 13 people in the Midwest and South.

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At least 20 homes were badly damaged and six people were hospitalized in the Chattanooga, Tenn., area after strong winds and hail lashed the area. To the east in Cleveland, Blaine Lawson and his wife Billie were watching the weather when the power went out. Just as they began to seek shelter, strong winds ripped the roof off their home. Neither was hurt.

"It just hit all at once," said Blaine Lawson, 76. "Didn't have no warning really. The roof, insulation and everything started coming down on us. It just happened so fast that I didn't know what to do. I was going to head to the closet but there was just no way. It just got us."

Thousands of schoolchildren in several states were sent home as a precaution, and several Kentucky universities were closed. The Huntsville, Ala., mayor said students in area schools sheltered in hallways as severe weather passed in the morning.

"Most of the children were in schools so they were in the hallways so it worked out very well," said Huntsville Mayor Tommy Battle.

Five people were taken to area hospitals, and several houses were leveled.

An apparent tornado also damaged a state maximum security prison about 10 miles from Huntsville, but none of the facility's approximately 2,100 inmates escaped. Alabama Department of Corrections spokesman Brian Corbett said there were no reports of injuries, but the roof was damaged on two large prison dormitories that each hold about 250 men. Part of the perimeter fence was knocked down, but the prison was secure.

"It was reported you could see the sky through the roof of one of them," Corbett said.

For residents and emergency officials across the state, tornado precautions and cleanup are part of a sadly familiar routine. A tornado outbreak last April killed about 250 people around the state, with the worst damage in Tuscaloosa to the south.

The Storm Prediction Center's Mead said a powerful storm system was interacting with humid, unstable air that was streaming north from the Gulf of Mexico.

"The environment just becomes more unstable and provides the fuel for the thunderstorms," Mead said.

Schools sent students home early or cancelled classes entirely in states including Alabama, Tennessee, Mississippi, Kentucky and Indiana. In Alabama alone, more than 20 school systems dismissed classes early Friday. The University of Kentucky, the University of Louisville and several other colleges in the state also canceled classes.

At least 10 homes were damaged in one subdivision in Athens, Ala. It wasn't immediately clear how many houses were damaged overall in the area. Homeowner Bill Adams watched as two men ripped shingles off the roof of a house he rents out, and he fretted about predictions that more storms would pass through.

"Hopefully they can at least get a tarp on it before it starts again," he said.

Not far away, the damage was much worse for retired high school band director Stanley Nelson. Winds peeled off his garage door and about a third of his roof, making rafters and boxes in his attic visible from the street.

"It's like it just exploded," he said.

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Contributing to this report were Associated Press writers Jim Suhr in Harrisburg, Ill., and Jeff Martin in Atlanta, Associated Press videojournalist Robert Ray in Cleveland, Tenn., and AP Radio's Shelley Adler in Washington.