POLICE eager to catch a yob who threw a stone through a train window have vowed to treat witness information confidentially.

Inquiries are also taking place after a distinctive silver mountain bike was found, which could be owned by the culprit.

Finding it lying on the platform at Marton, Middlesbrough, a train guard lifted it on board a Whitby to Middlesbrough train on Thursday evening.

As the train pulled away from the station, two youths emerged from under the platform. One wore a grey hooded top, the other a white top.

Another train stopped by the platform and the guard on the train was asked by a youth wearing a grey hooded top where his bike was.

A British Transport Police spokesman said: "As the train pulled out of Marton, the youth threw an object at the train, breaking a door window.

"Fortunately, this incident passed without any injury to passengers or train crew, but could well have been more serious."

The stone-thrower was white, in his mid teens and about 5ft 9in. The word Carbini was printed on his top.

The mountain bike is a silver Mongoose Travel Expert with black front forks.

Anyone with information is asked to call British Transport Police on 0800 405040.