A woman has died riding the Texas Giant roller coaster at Six Flags Over Texas in Arlington, just west of Dallas, a statement released by the theme park said.
The accident happened just after 6:30 p.m. Friday, the Associated Press reported.
Several media cited the park as confirming the death but with no explanation of how the woman was killed, nor who she was.
However, the Dallas Morning News quoted a witness, Carmen Brown of Arlington, who was waiting in line for the ride, as saying:
"She was right in front of us, but we weren't on the ride. The lady basically tumbled over... We heard her screaming. We were, like, 'Did she just fall?'"
Brown said the victim's young son was in the seat in front of his mother.
The Texas Giant is touted as the tallest steel-hybrid roller coaster in the world, and according to CNN is 153 feet at its highest point with a drop of 147 feet.
It was designed in 1990 as an all wooden roller coaster, CNN wrote, but redesigned with a steel track and reopened in April 2011.
Six Flags Over Texas spokeswoman Sharon Parker was quoted as saying:
"Since the safety of our guests and employees is our number one priority, the ride has been closed pending further investigation. Our thoughts and prayers are with the family and friends during this difficult time."