One man was taken to a hospital after being buried for hours in grain and debris in Hillsboro in southeast Iowa.

The bin - about 100 feet in diameter, 90 feet high and containing more than 500,000 bushels of corn - collapsed Monday evening. The force of the grain broke the walls of Jesse and Jennifer Kellett's home and sent the roof crashing down.

"The force actually took the house with the corn and shoved it and crushed it," Dan Wesely, Henry County chief sheriff's deputy, said Tuesday.

The Kelletts and their children, Jordan Walter, 11, and Sheyanne Walter, 9, were trapped. Jennifer Kellett and her daughter crawled out, but her husband and son - pinned by walls, wood and corn - had to be rescued.

Many residents of the town of 200 said they could hear the bin's rivets giving way, sounding like machine-gun fire. Farmers miles away reported feeling the ground shake. The bin was about 20 feet away from the house, authorities said.

The grain bin is owned by Chem Gro. The bin was new, Wesely said, and officials are investigating the cause of the collapse. A telephone message left with the company Tuesday was not immediately returned.

Emergency crews reached Jesse and Jordan Walters and supplied them with oxygen lines.

"The thing was they had to move this corn, and it kept rolling in. They had to move a lot of corn back before they could get down and find out what was holding them in. That would be the lumber, walls and different things," Wesely said.

Once free, Jordan Walters walked to an ambulance, where he was found to be uninjured. His father, rescued after about four hours, was taken to a hospital, which declined to release information about his condition.

"When it happened, my house shook, and I'm clear on the other end of this town," Hillsboro resident Naomi Sanderson told the Hawk Eye newspaper of Burlington.

(This version CORRECTS spelling of children's last name to Walter).)