An Ohio man was "critically injured" after he was struck by a fast-moving roller coaster at Kings Island amusement park in Mason, police said.

According to the Mason Police Department, a 38-year-old unidentified man suffered a critical injury after he was hit by the Banshee roller coaster at the park located roughly 30 minutes north of Cincinnati on Wednesday.

Police were called to a report of "a subject down on the ground in one of the restricted areas" by the 4,124-foot inverted roller coaster, which tops out at 68 mph.

Law enforcement said the male victim allegedly dropped his keys while riding on the coaster and entered the fenced-in restricted area to retrieve them.

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The man was "believed to have been struck by the ride" while he was in the restricted area, police said.

He was determined to have suffered a critical injury. 

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He was transported to a local hospital and then flown to the University of Cincinnati Medical Center for treatment.

It was not immediately clear the extent of the man's injuries.

Park guests on Reddit claimed to have seen the man before and after the incident, sharing their experience on the social media site.

"We were in the front row and towards the end of the ride, there was a man’s body lying face down on the grass below the coaster," a person wrote. "We don’t know if he was alive."

"This was my first year here, and I thought it was a prop to go along the Haunted Hill section of the amusement park," another wrote. "Does the banshee (sic) ride low enough to hit someone if they jumped the fence?"

The Banshee roller coaster will remain closed while officials investigate the incident, a park spokesperson confirmed to Fox News Digital.

"Kings Island’s focus continues to be on the welfare of the guest and his family," they said.