An investigation has been launched after reports that a group of children threw stones onto a road.
They accessed the old railway line, behind Nissan in Strand road.
Police are appealing for witnesses who might have seen the incident in the Broadgate area around 9pm on Sunday 28 January.
Stones were thrown at passing vehicles, shattering a rail replacement bus window, which sent glass across the seats.
The bus then continued on its journey to Blackpool.
Fortunately, there was no-one on the bus at the time of this incident.
A police spokesman said in a post to social media: “Do you know what your kids are up to tonight?
“We have had multiple reports of kids throwing stones at passing cars and buses in Broadgate.
“This bus luckily had no passengers but the results could have been worse.”
No arrests have currently been made.
Police are urging people to contact them on 101, quoting log reference 1451.