Children are being warned of the dangers of trespassing on railway lines as a youngster continues to fight for his life after being hit by a train.

Ben Woods' condition was this afternoon described as "serious" by staff at Middlesbrough General Hospital following Monday's accident on the East Coast Main Line.

The teenager, from Hurworth, near Darlington, lost his left arm in the accident and The Northern Echo understands surgeons at the hospital had to amputate his left leg.

He had been on the tracks, near Hilltop Farm, just south of Darlington, with a friend when he saw a train coming towards him. Stepping out of its way, he was struck from behind by another train going in the opposite direction.

The accident happened on Ben's 17th birthday.

David Henderson, headteacher at Hummersknott School, Darlington, where Ben sat his GCSEs a year ago, said the school had been deeply saddened by the accident.

Ben's sister, Carley is a year ten pupil at the school, and Mr Henderson said: "It is horrendous. I will be writing to his home and we are all here to do our best for Carley when she comes back.

"Everyone's just shocked and the school has taken the opportunity to have a go at kids about the railway lines."

He said the message was particularly important with the summer holidays coming up.

Staff at Darlington's Queen Elizabeth Sixth Form College, where Ben had just completed his AS level exams said they were "desperately sad" about what happened and felt "immense sympathy" for his family.

Principal David Heaton said: "Everybody who knows him, all his teachers and the teaching staff are really desperately sad that this has happened, because he's a very likeable young man.

"We were looking forward to him starting his A-levels in August." Ben had been studying sociology, English literature and law at the sixth form.

DC Rob Quarmby, of the Darlington branch of the British Transport Police, reiterated Mr Henderson's warning.

"The railway line is a dangerous place," he said. "Trains travel at high speeds and sometimes it's not as easy as people think to hear them coming and we urge people to stay off the lines."

A BTP freephone number, 0800 405040, is available for people to report anyone they see walking on the lines or acting suspiciously near railways.