Tiny Town, “the oldest kid-sized village and railroad in the USA,” was the site of a train derailment on Wednesday that left several people—young and old—with minor to moderate injuries.

The accident happened after the engine of the miniature train, which winds through a replica Old West town 20 miles southwest of Denver, tipped over, Dan Hatlestad of the Intercanyon Fire Department tells The Associated Press. All five open-roof cars behind the engine followed, leaving between 15 and 21 people hurt.

There were a few broken bones, Hatlestad tells 7 News, but “most of the injuries appear to be walking wounded,” or cuts and bruises. Some of the injured were taken to area hospitals.

Mark Techmeyer, a spokesman for the Jefferson County Sheriff’s Office, tells The Flume that an investigation is being conducted to determine the cause of the derailment. However, he adds, “Tiny Town has a wonderful safety record. As far as I know, they’ve never had a derailment.”