A theme park rollercoaster slipped off its track, an eyewitness claims, as he recalls hearing "horrific" screams.
Oakwood Theme Park in Pembrokeshire, south west Wales, was evacuated earlier this afternoon after a "serious" medical emergency.
The Welsh Ambulance Service was called to the scene at 1pm, with an air ambulance also arriving at the park.
The Health and Safety Executive (HSE) has since launched an investigation following the incident on the Treetops ride.
One eyewitness, who wished to remain anonymous, says he was among the first people on the ride but was told there would be a 10 minute wait as engineers were working on an issue.
"We waited for a bit and saw the engineers right in front of us doing some work," he said.
"We decided to come back in a bit. We returned 10 minutes later and saw people getting on the ride so we returned and sat near the front.
"Less than a minute into the ride I heard horrific screams and noticed the back end of the coaster slipping and sliding off the track and a girl crying in severe distress and what appeared to be the bar raised."
He added: "I shouted for the ride to stop and staff were clearly panicking to get it stopped. It went on for a bit before it grinded to a halt.
"We had to evacuate the ride on a bend and staff were present to help people off. I saw a mobile phone and a flip flop on the grass and realised someone must have come off the ride.
"A group of girls were in shock and I asked them if they were ok which clearly they weren't.
"When I went to retrieve my bag I saw a gentleman lying face down with a member of staff and a paramedic. He wasn't moving but staff later told me he was conscious and talking."
He added that an air ambulance arrived within 20 minutes and police officers were at the scene.
Within an hour, all visitors were reportedly told to leave the park and their details were taken by staff for a refund.
The site has remained shut since.
The Treetops ride is a family rollercoaster that travels through the woodlands that surround the park.
It is described as being "high up in the treetops" before twisting, bending and dropping through the tree canopy.
It is one of the site’s "most popular rollercoasters" and has been a feature of the park for nearly 30 years.
It has a top speed of around 22mph and stands just over 26ft high.
An air ambulance was seen leaving the park shortly before 4pm and headed in the direction of Swansea.
In a statement, Oakwood Theme Park said: “As a result of an incident at Oakwood today we have closed the park to the public with immediate effect."
Dyfed Powys Police confirmed that the HSE is leading the investigation.
A spokeswoman for the HSE said they had been made "aware" of an incident at the theme park.
It has been confirmed that one person was taken to hospital and details surrounding what had happened are being looked at by officials.
A statement from Oakwood Theme Park provided to the Mirror confirmed: “As a result of an incident at Oakwood today we have closed the park to the public with immediate effect.”
