An investigation is under way after youths threw an iron bar on to a railway line.
As the bar hit the line at Angmering station at 9.30pm last Wednesday it caused a short-circuit.
Trains along the South Coast were held up for almost an hour while emergency repairs were carried out.
PC Sarah Yarnall, of British Transport Police in Brighton, said: "We have CCTV footage that we are looking at and think we have the offenders on film.
"This was a very dangerous thing to do and the youths could have easily been hurt. They also caused damage to the railway line and disruption on the network."
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