A woman who fell to her death from a 14-storey roller coaster at a US theme park had complained to staff that her safety lap bar was not properly secured just moments before she was flung off the ride, according to a witness.
Rosy Esparza was riding the Texas Giant roller coaster, the tallest steel-hybrid roller coaster in the world, with her two children when she plummeted to her death on Friday evening at the popular Six Flags Over Texas theme park in Arlington, Texas.
It's very sad that I lost my mum, but I'm happy that I was able to enjoy her to the maximum while she was alive.
Witnesses said Mrs Esparza's son and daughter were hysterical when their roller coaster carriage pulled back into the station without their mother at the end of the ride.
The Texas Giant roller coaster at Six Flags Over Texas where a woman fell to her death. Photo: AP
“My mum! My mum! Let us out, we need to go get her!” they repeatedly screamed to staff as the carriage came to a stop.
The roller coaster is believed to have made its first descent and was rounding the first corner at speed when the Dallas mother flew off the ride.
One witness, Carmen Brown, told the Dallas News that Mrs Esparza had expressed concern that her safety restraint was not properly secured, but that a Six Flags worker had assured her that she was fine.
Rosy Esparza died after falling from a rollercoaster.
“She was nervous and panicking,” Ms Brown said.
Joshua Paul Fleak tweeted that he was sitting behind Mrs Esparza on the same ride when he saw the tragedy unfold.
"Literally just witnessed someone fly off the Texas Giant two seats in front of me," he tweeted. "Restraint came undone, coaster turned and she was gone."
Nadine Kelley was lining up to ride the roller coaster when the carriage pulled back in, without one of its passengers.
"When it pulled up, the daughter and son of the lady that flew out of the car were hysterical and were saying that their mother flew out of the car," Ms Kelley told Reuters.
"The people working there didn't really know what to do...
"The guys that were sitting right behind the lady said that right when they came down off the first bump and hit that first turn, she flew out."
Paramedics responded to the accident about 6.45pm local time and pronounced Mrs Esparza dead at the scene.
The Arlington, Texas, Police Department is investigating the incident, and the ride has been closed until it is complete.
Mrs Esparza's son, Amado, wrote in Spanish on his Facebook page that his mother had lived life to the fullest, and that her death was "like a nightmare that I can not wake from".
“I've never discovered a day as long as this one," he wrote.
"It's very sad that I lost my mum, but I'm happy that I was able to enjoy her to the maximum while she was alive.”
The attraction has been closed since the incident, Sharon Parker, a spokeswoman for Six Flags Entertainment, said.
“We are committed to determining the cause of this tragic accident and will utilise every resource throughout this process,” she said.
“It would be a disservice to the family to speculate regarding what transpired. When we have new information to provide, we will do so. Our thoughts, prayers and full support remain with the family.”
The Texas Giant debuted in 1990 as a wooden roller coaster, and was rebuilt and re-introduced in April 2011 as a hybrid wood and steel roller coaster, according to the park's website.
It measures 1500 metres in length and its highest elevation is 14 stories, according to the website.
Mrs Esparza is the second person to die on a ride at the theme park since it opened in 1961. Another woman drowned in 1999 when a Roaring Rapids raft capsized, according to the Dallas News.