THREE children are in a serious condition in hospital after a rollercoaster derailed at the popular M&Ds theme park in Lanarkshire.

Eyewitnesses said the Tsunami ride at the Motherwell amusement park had been full when it came off the track injuring eight children and two adults.

Four children are being treated at the Royal Hospital for Children in Glasgow, with three described as serious and one in a stable condition.

An adult is being treated at the Glasgow Royal Infirmary and is in a stable condition.

The other five casualties were being treated in hospitals in Lanarkshire. One adult and a child were described as stable, while three other children were due to be released this evening.

Police, firefighters and paramedics rushed to the scene as several visitors posted images on social media appearing to show a mangled carriage on a pathway surrounded by dozens of people.

Chief Inspector David Bruce said: "Along with other emergency services we attended immediately and on arrival it became clear that a series of five gondolas connected on a train on the Tsunami ride have detached from the rails, struck the superstructure and then struck the ground.

"We have launched an investigation and an inquiry between Police Scotland and the Health and Safety Executive (HSE)."

Mr Bruce added: "They (the gondolas) fell less than 20 feet. It would appear that they have been coming round a bend and at that point it has detached.

"At this stage it's very, very early in the inquiry and we are still taking witness statements but the gondola had been in operation on the rollercoaster and it would appear that it has been coming round a bend.

"It's an inverted rollercoaster which means that the riders hang in gondolas below the rails rather than sit above them.

"It would appear to come off as it has come round a corner. It struck the ground but it hadn't struck anything on the ground.

"I don't know what speed it would have been travelling but it was operating and rollercoasters do travel at speed."

In one image, taken by Dean Borris, people can be seen trapped upside down in their seats on the carriage, with their legs protruding into the air.

Scott Nailon was one of the first on the scene, seconds after the crash. The 38-year-old from Hamilton was at the park with his two children and had left the Tsunami queue a few minutes before the accident.

He told The Herald: "It was bedlam. Absolute pandemonium. The M&Ds staff were just telling folk to stay back but offering no assistance or even assurance to the kids who were trapped.

"I'm a trained first aider and with a few others were went straight to the kids in the ride. A chef from the place had some alan keys and was able to get one girl out while he held the carriage up.

"A doctor who'd been at the park then arrived and was with a young boy who was definitely a priority. His injuries looked really bad.

"Maybe 15 later the fire crews arrived and the ambulances so we just took a step back at the stage.

"But it was brutal. One guy who'd been on the ride was about 20 metres away from it."

The area was sealed off as Police Scotland CID officers and the Health and Safety Executive carried out preliminary investigations.

A HSE spokesman said the agencies primary role was "to provide assistance".

Katie Burns said she had just finished riding the Tsunami rollercoaster and was walking past when the carriage crashed with children on board.

On Facebook, she said: "Literally got off the Tsunami at M&Ds and then walking past and the next lot of people get on and the full thing goes off the tracks.

"Honestly never been so scared in my life, with this weather they should not be on.

"Kids and adults are still on it upside down, it's like something out a horror film, children crying and everything.

"Literally can't believe this, my heart goes out to everyone on it, a full load came off the track but and on the pavement, like a horror film worse thing ever heard and seen, can't get over this."

She posted an image of one of the rollercoaster wheels on the pavement.

Witness James Millerick, who was queuing for another rollercoaster at the theme park, said he heard "shrieks" from customers.

He said there was talk that someone had come off one of the rides and rushed over.

"When we got there the rollercoaster had come off the track entirely - straight through the gated fence at the side of the rollercoaster and was upside down on the concrete path at the side," he told Sky News.

"There were maybe seven or eight individuals, mostly of younger age between maybe 10 and 15 years old that were actually trapped inside the rollercoaster lying on the ground. The harnesses were still on as well so there was absolutely no movement."

He said he thought the rollercoaster had slipped off the tracks as it came around a corner but did not fall from the highest point.

A spokesman for the Scottish Ambulance Service said six ambulance crews, a specialist operation team and emergency doctors were on the scene.

He said: "I can confirm that we are attending an incident at M&Ds theme park in Motherwell."

According to the M&D's website, the Tsunami rollercoaster can go at speeds of up to 40 miles per hour through corkscrew turns and loops on a 650km track.

Children under 10 are not allowed to use the ride, and under 14s must be accompanied by a paying adult.

First Minister of Scotland Nicola Sturgeon said: "My thoughts are with everyone involved in this terrible incident at M&D's theme park, especially those injured."

Ruth Davidson, leader of the Scottish Conservative Party, said: "Awful news coming from M&Ds. Deeply concerning - our thoughts are with those affected and with emergency responders."

A spokesman for M&D’s said: “As family-run business, our thoughts are with those who have been injured and their families. We wish everyone a full recovery.

“We are cooperating fully with Police Scotland and the Health and Safety Executive (HSE) on their joint investigation to ascertain the cause of the accident.”