"There was blood all over the floor because it was pouring out of their legs in the carriage"
Alton Towers will remain closed until the cause of a rollercoaster crash which left 16 people injured is discovered, the theme park's chief has said.
The attraction's gates are shut for a second day while the Health and Safety Executive looks into why two carriages collided on the Staffordshire venue's ride, The Smiler, at around 2pm on Tuesday.
Nick Varney, chief executive of Merlin Entertainments, which runs the resort, said the park could only reopen when the investigation had concluded but did not give a time-frame.
Writing in the Sun, he said: "At this point I don't know if it was a technological or a human error. We want to know if this issue is isolated to The Smiler. We can't open again until we're sure."
A total of 16 people were hurt - including two men aged 27 and 18, and two women aged 19 and 17, who suffered serious leg injuries.
Among those on board was Vanisha Singh, who was in the second row of the carriage with her mother Chanda, 49, and her sister Meera, 26.
She told the Sun there had been "technical difficulties" moments before they embarked on the fateful ride, as several test cars were sent ahead of them.
"We finally went up and were kept at the top for 10 or 15 minutes chatting, joking that we were the guinea pigs," the 29-year-old said.
Describing the crash, she added: "The metal safety bar smashed into our legs. There was loads of screaming. I felt a burning sensation in my pelvis, and back and neck pain.
"It was terrifying. There was blood all over the floor because it was pouring out of their legs in the carriage and dropping down. The doctors and firemen were covered in blood as they scaled the scaffolding to treat the guys on the front row."
Warning: Video contains strong language.
Ms Singh, who was sat behind Joe Pugh, an 18-year-old textile design student at the University of Huddersfield, said his girlfriend Leah Washington had to be given a blood transfusion and morphine before she passed out following the collision.
The Oaks Working Men's Club in Mr Pugh's home town of Barnsley, South Yorkshire, posted on Facebook: "After hearing the news about the terrible accident at Alton Towers it has to come to our attention that a member of our staff was involved.
"We at the Oaks WMC would like to extend our prayers and best wishes in the speedy recovery of our barman Joe Pugh and his girlfriend Leah Washington."
An Alton Towers spokesman said: "The decision has been taken that Alton Towers theme park will remain closed on Thursday following the incident on The Smiler.
"Guests with pre-booked tickets and those arriving at the theme park will have the choice of a full refund or an alternative dated ticket.
"Guests with pre-booked tickets have the option to use their tickets tomorrow at an alternative attraction. See website for more info."
Witnesses described scenes of horror after the collision, with one victim's face covered in blood and others screaming in terror.
Jack Carver, 33, told reporters: "It was like a horror movie hearing those screams.
"There was pure terror in their voices. It reminded me of Final Destination where the rollercoaster comes off the tracks. It was really scary."
The four people who suffered critical injuries were airlifted to major trauma centres after the 16 occupants were rescued from 25ft up in the air at an angle of about 45 degrees.
Some of the occupants suffered an ordeal which lasted more than four hours, with the evacuation not complete until 6.35pm.
The £18 million rollercoaster, which boasts a world record 14 loops, has been closed twice because of safety concerns since opening two years ago.
In July 2013 it was closed after reports that a bolt was seen to have fallen from the ride and in November that year the rollercoaster was closed after plastic guard wheels came loose and hit front-row riders.
Following the accident, Merlin Entertainments was the biggest faller on the FTSE 100, with shares down 3%.
The firm, based in Poole, has run Alton Towers since buying out previous owner the Tussauds Group in May 2007.