Local residents in Newtongrange, Midlothian, have witnessed an increase in youths throwing items of the Lothian Bridge Viaduct onto the caravans and buildings below.
The incidents are reported to be happening between 3pm and 5pm on weekdays, as well as various times over the weekend.
Objects including tree stumps, stones and branches have been thrown from the viaduct by children who are believed to be of early secondary school age.
Anyone who witnesses suspicious activity in the area, or who can assist the police in identifying those responsible are asked to come forward.
A Police spokesman said: “The youths who have participated in this mindless act of stupidity not only put any individuals at the bottom of the viaduct in danger, but they are at risk themselves by acting recklessly at a partly exposed bridge parapet.
“Officers are engaging with the Newtongrange community and will speak with local youths to highlight the dangers of this behavior and to trace those involved.
“If anyone witnesses youths throwing items from the viaduct they should contact police immediately.”
Anyone with any information can contact Lothian and Borders Police on 0131 311 3131, or the charity Crimestoppers in confidence and complete anonymity on 0800 555 111.