ARLINGTON, Texas (AP) — Investigators will try to determine if a woman who died while riding a roller coaster at a Six Flags amusement park in North Texas fell from the ride after some witnesses said she wasn't properly secured.

The accident happened just after 6:30 p.m. Friday at Six Flags Over Texas in Arlington. Park spokeswoman Sharon Parker confirmed that a woman died while riding the Texas Giant roller coaster — dubbed the tallest steel-hybrid coaster in the world — but did not specify how she was killed.

Witnesses told local media outlets the woman fell. The woman's name has not been released.

"She goes up like this. Then when it drops to come down, that's when it (the safety bar) released and she just tumbled," Carmen Brown of Arlington told The Dallas Morning News. Brown said she was waiting in line to get on the ride when the accident happened. She witnessed the woman being strapped into the ride.

"They didn't secure her right. One of the employees from the park — one of the ladies — she asked her to click her more than once, and they were like, 'As long you heard it click, you're OK.' Everybody else is like, 'Click, click, click.' " Brown told the newspaper.

"Hers only clicked once. Hers was the only one that went down once, and she didn't feel safe, but they let her still get on the ride," Brown said.

Six Flags expressed sadness over the death and said the ride would be closed Saturday.

"We are working closely with authorities to determine the cause of the accident," Parker said in a statement Saturday. She also said a concert scheduled for Saturday had been canceled.

Arlington police Sgt. Christopher Cook, the department spokesman, referred all questions to Parker. A message left for Parker by The Associated Press was not returned. No other details were available.

The Texas Giant is 14 stories high, and has a drop of 79 degrees and a bank of 95 degrees. It can carry up to 24 riders. It first opened in 1990 as an all-wooden coaster but underwent a $10 million renovation to install steel-hybrid rails and reopened in 2011.

When the car that the woman had been riding in returned to the loading zone, two people got out and were visibly upset, Rockwell resident John Putman told the Fort Worth Star-Telegram.

"They were screaming, 'My mom! My mom! Let us out, we need to go get her!" Putman told the newspaper.

Also Friday, an Ohio amusement park's thrill ride malfunctioned when a boat accidentally rolled backward down a hill and flipped over in water, injuring all seven people on it. Operators stopped the Shoot the Rapids water ride after the accident, said officials with Cedar Point amusement park in Sandusky, Ohio.

Six Flags Over Texas opened in 1961 and was the first amusement park in the Six Flags system. It is 17 miles west of downtown Dallas. The park's first fatality happened in 1999. A 28-year-old Arkansas woman drowned and 10 other passengers were injured when a raft-like boat on the Roaring Rapids ride overturned in 2 to 3 feet of water.