A Bradford head teacher was today desperately pleading for news of her son who disappeared after a terrifying late-night phone call.

The last Anne Plunkett heard of her son David was a harrowing conversation on his mobile after he had lost contact with his friends on a night out in Manchester.

It is now four days since the 21-year-old student disappeared, and his family and police are becoming increasingly concerned for his safety.

Police divers were yesterday brought in to search Manchester's Bridgewater Canal which runs close to the Daytona Racetrack on the sprawling industrial estate where the big clubbing event that David and his friends attended was held.

Mrs Plunkett has been at the scene with family and friends ever since helping police with the massive search.

His mum, who is head teacher at Reevy Hill Primary School, Buttershaw, last heard from David in the early hours of Sunday morning when she called him on his mobile.

His friend had phoned them at their home in Shelf to say they had got separated so Mrs Plunkett rang her son and exchanged a harrowing conversation before they called the police.

Mrs Plunkett, said: "He was talking directions to himself saying "turn right, turn, right", then he suddenly started howling as though he was being attacked.

"It was a horrendous noise. He wasn't coherent. My husband took the phone off me and we rang the police and we have heard nothing since."

David and friends had been at the Budweiser King of Clubs show at Trafford Park, Manchester, on a coach trip from Leeds on Saturday but he never made the return journey.

David, a former pupil at Buttershaw High School, is now in his final year studying Events Management at Leeds Metropolitan University.

Police were hoping the thousands of fans at Old Trafford last night for the game against Charlton Athletic may help in the search for David who has never gone missing before and whose disappearance is described as "out of character".

Mrs Plunkett believes he never took drugs but says he might have been given something or had his drinks spiked which led to him becoming so disorientated.

"We are pinning our hopes on the fact he was out of his head and that he will turn up.

"This is horrendous. You see things like this on television and wonder how the parents cope then suddenly you find yourself in it. Yes, he is 21 but he is still my son and he is missing. We are devastated.

"Something has happened to him and not knowing is the worst thing. As time goes on you try to keep optimistic but something must have befallen him.

"He is not a drug user, the police have checked all that out thoroughly. On the whole he is very responsible."

David organised an abseil by the Lord Mayor of Bradford Coun Allan Hillary down the Central Library on Valentine's day as part of his course work at the university where Bradford councillor David Ward is his personal tutor.

Coun Ward, who has known him for two years, said: " David is the salt of the earth and so close to finishing his course.

"I am certain that he would not be involved in anything crazy, he is not that sort. I cannot think what has happened.

"You just think, where is he? There must have been hundreds of people around at the time."

David is 5ft 11 inches, of average build with dark brown swept back hair which is collar length at the back. He has long thin sideburns and was wearing silver oblong small-frame silver glasses.

He was wearing black trousers with pale pink pinstripe in them and a red/pink shirt. He has a silver ring on his right hand and a silver bracelet.

His driving licence, used as age confirmation, has been found at the venue by security staff but there has been no other trace.

Police are tracking down the whereabouts of his phone as it is still taking messages.

His friend Michael Vittas who he travelled to the event with and who first raised the alarm by contacting the family has joined the search every day.

Mrs Plunkett added: "If anyone knows what happened to him please contact the police. Something has and we need to know what."

West Yorkshire Police are liaising with Greater Manchester Police in the search. Anyone with information should contact Calderdale Police on (01422) 337059.