Mindless thugs put innocent passengers' lives at risk and caused a "blinding explosion" after pushing a bike on to tracks in front of an oncoming passenger train.
The collision sent sparks flying as the bike hit the electric live rail - and the scene was caught on camera at the level crossing at Bedhampton station in Hampshire.
British Transport Police played back CCTV tapes and saw two youths ride across the track, and them, out of shot, one of the bikes was left on the tracks.
It is not known whether the youths were deliberately trying to derail the Southern train, which runs from Barnham to Portsmouth and Southsea.
Inspector Mick Morriss said: "CCTV captured two youths riding across the level crossing at 1.34am.
"Seconds later, out of shot, one of the bikes is pushed back towards the crossing - we believe deliberately - landing on the tracks.
"Two hours later it was struck by the early morning 3.34am Southern service from Barnham to Portsmouth and Southsea, causing an explosion and sending a blinding shower of sparks flying into the air.
"I simply cannot over-emphasise enough the dangers of this type of crime. Trains travel at high speeds and there is a very real risk when they strike objects on the track that they could be derailed."
He added that he would like to hear from anybody that had any information about the incident.
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