Police have received multiple reports of youths throwing stones from a Sheffield bridge.
Officers said they had received information missiles were being thrown from the railway bridge on Herries Road close to Hillsborough Stadium.
The track is live with passing freight trains and officers are concerned the group of youngsters are putting themselves at risk.
"A spokesman from Sheffield West Neighbourhood Police Team said: "We have received a number of reports about youth throwing stones and other items from the railway bridge on Herries Road.
"Officers have been giving it passing attention and will be working with other colleagues to try to identify anyone involved. These track are still live so not only are these people causing damage and a danger to other but they are also putting them self at risk.
"Trespassing on a railway line is an offence and we will be working alongside British Transport Police in relation to this."