Warning: This article contains some graphic details
One person has died and others were injured after an incident on a rollercoaster at an amusement park in the US state of Georgia.
The Cobb County Police Department is investigating Monday's death at Six Flags Over Georgia, about 15 miles (24km) from Atlanta.
The ride involved has not been specified but aerial footage from news helicopters showed the Goliath rollercoaster stopped midway, with riders being helped off by workers.
Horrified witnesses have told local media they saw a man ejected from the ride and police say preliminary information indicates this was the case.
Six Flags said it was temporarily closing nine rides across the US and Canada as a precaution.
It said it was "deeply saddened by the guest incident at our park today. Our thoughts and heartfelt condolences are with the guest's family, friends, and loved ones".
The Cobb County Police Department said the incident happened just before 16:00 local time (20:00 GMT) on Monday.
It said officers working at the park found the man, identified as Atlanta resident Hassan Jihad Ibn Kariem, 42, beneath the ride. He was unresponsive and not breathing.
"Preliminary information gathered through witness and employee interview indicates Kariem was ejected from the ride and struck other patrons before falling beneath the attraction," police said in a statement.
The Office of Commissioner of Insurance and Safety Fire, which enforces amusement park safety rules and standards in Georgia, said it was also reviewing the incident "to ensure full compliance with all applicable policies and procedures".
Local outlet 11 Alive quoted a witness saying Kariem had come loose from his seat and had then struck the rollercoaster and some of his fellow riders before falling onto the roof of a nearby haunted house attraction.
The incident was captured in souvenir photos that were automatically taken of the rollercoaster while it was in motion, the witness added.
A husband and wife, who were on the ride, also told 11 Alive that Kariem fell from the ride and was struck by it. They said workers at the park had checked their safety harnesses before the ride set off.
"We were having a great time and to just screaming 'Oh my God, what is happening?'," the woman said.
Another witness, CiCi Nelson, told CNN she was in line to ride Goliath when the rollercoaster returned and she saw an empty seat with a loose safety bar and a girl covered in blood.
Nelson described a scene of hysteria, adding that one man was "freaking out, saying someone fell off".
Brittany Landry, who believes she saw the man ejected from the rollercoaster, told Fox News she was in tears.
"I broke because we were just on there," Landry said.
A park spokesperson said in a statement that its team and local authorities had responded immediately and that they were cooperating on an investigation into the incident.
Mableton Mayor Michael Owens said the city's public safety director was also coordinating with local police and park security on the situation.
The death at Six Flags Over Georgia is at least the seventh there, according to the Doan Law Firm, which tracks amusement park accidents and represents victims.
The Goliath ride opened in 2006, and it has an elevation of 200ft (60m), a 170ft plunge, a 540-degree spiral, and a speed of up to 70mph (112km/h), according to the park website. On its "thrill scale", Six Flags ranks Goliath at level four out of five.
Brian Avery, a University of Florida professor with an expertise in amusement ride and device operations, told the BBC that rollercoasters are not federally regulated, leaving it up to states to determine the necessary safety protocols and maintenance procedures.
"When these types of tragedies happen, you got to get to the bottom as to why, so we can move forward and address those issues so that they never happen again," Avery said.
He explained that one of the main factors considered when designing a rollercoaster is how to contain the rider. This specifically includes determining where to place their harness - something that changes depending on the ride type.
"We design these rides, the industry does, to flirt with danger," Avery said. "We're taking people up to the edge, but we're not actually putting them in danger. That is the goal."
Six Flags is the largest amusement park operator in North America, with 20 amusement parks, 14 water parks and nine resorts across Canada, the US and Mexico.
The death in Georgia comes just weeks after one of Six Flags' parks in southern California announced it would close the popular X2 roller coaster after more than 100 people alleged brain injuries from the ride.
Six Flags said that ride had passed a range of safety tests, but that it had decided to retire the attraction because it was "the right thing to do".
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