Passengers on a Preston Bus narrowly escaped injury after yobs hurled an object through their window.
The number 35 bus to Tanterton was travelling along Fylde Road, when it was targeted by vandals who smashed a window with an object at around 7.15pm on September 26.
Passengers reported seeing between 10-15 teenagers around at the time of the incident.
Nobody was injured during the attack but the bus had to be removed from service, said a representative for Preston Bus.
The driver of the bus was praised for ensuring her passengers were all fine and the bus company sent a replacement bus within 10 minutes of the incident.
Thomas Calderbank for Preston Bus said: "There was an incident onTuesday evening involving a bus on service 35 where a window was broken.
"The driver ensured all passengers were OK before contacting the controller to send another bus.
"Incidents such as this come in fits and starts, we can get two or three windows broken in one evening and then go for months without anything happening."
Officers are now appealing for anyone who may be able to help them with their investigation to get in touch.
A police spokesman said: "We received reports of objects thrown at a moving bus causing a window to smash.
"The offenders are then believed to have made off. If you have information that may help our investigation then please get in touch. "
Anyone with information can contact police on 101 quoting crime reference number SA 1715176