Police have released images of three boys they want to trace after a train hit concrete debris on a railway line.
It was the sixth time that such debris had been dumped on tracks in Croston, Lancashire.
The latest incident took place near Ridley Lane at 5.20pm on Wednesday August 14.
A train struck the debris but fortunately without incident, said British Transport Police (BTP).
A BTP spokesman said: “Placing items on the tracks is extremely hazardous. Those involved are endangering their lives and could possibly cause severe damage to trains.
“Officers believe those pictured may have information that can help their investigation.”
Anyone who knows the identity of those pictured is asked to contact BTP by texting 61016 or by calling 0800 40 50 40 and quoting reference number 440 of 14/08/19.
Alternatively, call Crimestoppers anonymously on 0800 555 111.