The train, carrying passengers, was passing through Coatham Marshes, Redcar, when the incident happened at about 12.30pm on Saturday.
Luckily there were no injuries as a result of the incident but officers say it “could have been much worse”.
The impact caused a football-sized dent.
PC Gary Sykes, the investigating officer, said: “The train was passing through Coatham Marshes around 12.30pm on Saturday, November 30, when a boulder was thrown from a footbridge which crosses over the tracks.
“The boulder-type rock landed on top of one of the carriages, which was carrying passengers at the time, causing a dent the size of a football.”
Officers attended the area following the report and carried out a full search of the area but no suspects were found. There was no disruption to services.
Officers are now carrying out a number of inquiries including speaking to witnesses and urging anyone with information to come forward.
PC Sykes added: “The train driver, who reported the incident to police, saw a boy, aged between 13 and 15, wearing a dark coloured hooded top run from the scene, and we are very keen to speak to him.”
Anyone with any information should contact British Transport Police on 0800 405040 or Crimestoppers anonymously on 0800 555 111 quoting NEA/B5.
Article from the Gazette Live