Boys wanted after train hit concrete left on rails near Croston
Police are searching for three boys after a train hit concrete debris which had been dumped on a railway line.
British Transport Police said the debris was left near Ridley Lane in Croston, Lancashire, at 17:20 BST on 14 August.
A spokesman said it was the sixth time concrete had been left on the tracks.
He added that while the train had hit the debris "without incident", placing items on the tracks was "extremely hazardous".
Appealing to anyone with information to get in touch, he added that those involved had also been "endangering their lives".