Cedar Point's Magnum XL-200 is closed, pending further investigation of an accident Saturday that left three riders in need of minor medical attention, said park spokesman Robin Innes.
Magnum was shut down around 11 a.m. Saturday after a train loaded with people bumped into another train full of people.
Two people were treated in the park's first aid station and later released, and another was sent to Firelands Regional Medical Center for asthma related problems. That person was released later in the afternoon, said Innes, the park's director of public relations.
Hospital officials would not confirm the person's condition Saturday.
The train might have failed to completely stop in the braking area when it hit the train ahead of it, Innes said. He said the train was traveling less than 10 mph when it hit the other train.
"We won't really know until we complete our review," Innes said. The coaster could open soon but it will depend on the progress of the review, he added.
Both trains received minor damage to their fiberglass bodies, he said.
Since the Magnum opened in 1989, there has not been any problems with the coaster until now, Innes said.
The Magnum stands 205 feet tall and can reach speeds of 72 mph. The coaster features 5,106 feet of track and was voted No. 3 in the "Best Steel Coaster in the World" category in a poll conducted by Amusement Today.
In its 18 seasons, more than 36 million people have ridden the Magnum.