A bus was pelted with stones as it travelled through Grangemouth on Saturday evening.
The incident took place in Bowhouse Road, near the junction with Kingseat Avenue, at around 6.20 p.m.
Several stones were thrown at the H4 Denny - Brightons service, with the rear window being smashed.
PC Frazer McFadyen, who is investigating the incident, said: “This was a very dangerous and reckless act of vandalism which took place in an area that would have been busy at the time.
“The consequences could have been much more serious, and what may have been thought as a bit of fun was a serious incident that could have affected other road users as well as the passengers.
“I am appealing for the two passengers who were on the bus, and anyone who may have seen the incident, to call us so we can identify the vandals and bring them to justice.”
Anyone with information should call Central Scotland Police on 01786 456000, or details can be given anonymously by calling Crimestoppers on 0800 555111.