James Cook reports from the scene of the crash in South Lanarkshire
A schoolgirl who died when a coach carrying a party of teenagers on a trip to a theme park crashed in South Lanarkshire has been named by police.
Natasha Jade Paton, 17, from Cleghorn, near Lanark, was in a group from Lanark Grammar School heading for Alton Towers in Staffordshire.
Their coach overturned in "horrendous" weather conditions on a bridge on the A73 at Wiston, south-west of Biggar.
All of the passengers received hospital treatment, three for serious injuries.
NHS Lanarkshire said a total of 44 people had received hospital treatment following the crash and 19 remained in various hospitals around Lanarkshire and Glasgow.
A spokeswoman for the health board said all the patients were in a stable condition.
Natasha Paton died in the crash near Biggar in South Lanarkshire
Police said the 17-year-old was thrown from the bus and trapped under it.
She and one other person with leg and chest injuries were airlifted to the Southern General Hospital in Glasgow.
Tribute messages have been left by friends on Miss Paton's Bebo website.
One read: "You were an amazing girl, who everyone will miss."
The site also has photographs of the 17-year-old on a previous trip to Alton Towers.
Thirty-nine pupils, five members of staff and the driver were on the coach when it crashed.
A spokesman from RAF Kinloss said they scrambled the Royal Navy Sea King from Prestwick just before 0610 BST.
The accident happened as the bus approached a left-hand bend.
It lost control and fell 10ft into the river, crashing through the bridge wall.
Fire and rescue service were forced to rescue the passengers through the coach's sun roof.
The driver was trapped inside the bus and had to be stretchered out by emergency workers.
Supt Iain Murray, head of road policing for Strathclyde Police, said: "Our hearts and our thoughts go to the families and those who have been seriously injured."
Mr Murray said the exact cause of the accident was still under investigation, but given the weather conditions in the area, snow "had a part to play".
He said a structural assessment of the bridge was being carried out.
Strathclyde Fire and Rescue's assistant chief officer Jim Doyle said his crew arrived to a "very arduous scene".
At this moment, our major focus is on the young people, their families and staff within the school
Larry Forde Education director, South Lanarkshire Council
The bus involved in the crash was operated by Lanarkshire-based company Photoflash.
Miss Paton was identified by a teacher and police said her relatives had been informed.
Eyewitness Bill Ward, of Wiston, said the coach had ended up on its side in a burn.
"The conditions here are absolutely atrocious and the roads are very, very slippy," he said.
Local resident Mark Attwood was woken by the sound of the crash and helped look after some of the pupils involved.
He said: "There was a knock at the door and a gentleman said could we take a couple of school kids in because there had been accident.
"They were visibly shaken and tearful, and very emotional and upset. Later they were all moved to the village hall."
He added: "It happened so close to my house and my own children use that route. I'm very shaken up."
A Royal Navy helicopter airlifted the injured to hospital
Strathclyde Police asked parents of the pupils involved in the crash to go to Lanark Grammar School for further help, not the scene of the accident.
Pupils at the school were sent home for the day.
The trip to Alton Towers was organised by the school annually as a pre-Easter break from exam preparations for sixth-year pupils.
South Lanarkshire Council's education director Larry Forde said: "Our thoughts and prayers are with the family of one of our senior students at Lanark Grammar who died this morning, and all who were injured.
"The head teacher Mark Sherry and everyone connected with the school wish to express their sympathies to all those involved.
"At this moment, our major focus is on the young people, their families and staff within the school."
He added that social workers and counsellors were at the school to help staff offer support to the families of those involved.
Susan Thornton's son Adam was supposed to be on the trip but she told BBC Scotland she stopped him going because of the weather.
"I just said the roads were too treacherous, that they shouldn't make the journey, " she said.
"He said to me he woke up at four anyway because he was desperate to go. He wanted to be with his friends and have a nice time but he said at four he knew he couldn't go."
The coach fell through the bridge into the river below
She added: "I am very relieved but I'm also very upset for all the people that are involved."
First Minister Alex Salmond said the crash was "almost certainly weather-related".
He added: "Our thoughts are very much with the parents and relatives and staff members caught up in this incident.
The local MP Jim Hood described the accident as "shocking and terrible".
He said: "My thoughts and prayers are with the staff and pupils involved and their families. What was supposed to be an enjoyable trip to Alton Towers has ended in horrific circumstances."
Mr Hood praised the emergency services staff who responded to the accident in difficult weather conditions.
Prime Minister Gordon Brown also said his thoughts were with those involved in the crash.
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