DEKALB, Ill. -- A monster truck performing stunts in front of an auto parts store veered into a crowd of spectators Thursday, injuring at least nine people, officials said.

All were in fair condition at hospitals, and one person was being evaluated for possible admission, said Sharon Emanuelson, a spokeswoman for Kishwaukee Community Hospital in DeKalb.

Another three people refused medical treatment, Fire Chief Lanny Russell told The Daily Chronicle of DeKalb.

As part of the demonstration in a monster truck tour sponsored by auto parts dealer Napa, the truck drove over and crushed four cars.

The truck became airborne over the vehicles after the driver revved the engine on the fourth pass, and when it landed, it did not stop and plowed through the crowd, witnesses told the paper.

The truck then knocked down part of a wooden fence and crossed railroad tracks before striking a chain-link fence, the witnesses said.

“There was just this sound of steel crunching,” DeKalb resident James Vesely said. “I ran over to see if it hit anybody’s car, and I saw a woman and a little girl around 3 years old lying on the ground with dirt on them.”

Napa officials at the scene declined to comment to the newspaper.

The Associated Press left a phone message for a spokesman for Napa’s parent company, and the telephone at the auto parts store near the accident site was busy. DeKalb police would not immediately comment.

The manager of a bicycle shop on the block where the accident happened said he didn’t see the incident but saw the truck performing stunts beforehand, and estimated at least 100 people were watching.

“It looked very precarious,” said Tobie DePauw, manager of North Central Cyclery.