In the span of less than a week this July, surgeons at a Southern California hospital raced to save the lives of two women suffering from alarmingly similar brain hemorrhages.

The severe injuries were the kind doctors encounter in patients after high-speed collisions or other violent accidents that cause the brain to twist and slam inside one’s skull.

Neither woman, however, had been involved in a crash, fall or other such incident.

Instead, they had ridden an extreme roller coaster at Six Flags Magic Mountain, known as X2, which draws thrill-seekers from around the world with its rotating seats, near-vertical drops and unpredictable movements. It has long been the park’s marquee attraction — promoted as a “[rite] of passage for the ultimate daredevil.”

But behind the ride’s legendary reputation lies a troubling record of serious injuries, a CNN investigation has found.