About 10.30pm on February 18, officers were told a group of people threw rocks from the railway overpass at Bridge Street onto oncoming traffic.

The rocks caused damaged to three vehicles traveling on the roadway below.

A B double truck suffered damage to a rear window, another B double truck suffered dents and paint damage to its roof, and the front windscreen was smashed on a Nissan Murano SUV.

No one was injured.

Officers from Hunter Valley Police District were notified and started an investigation into the circumstances surrounding the incident.

Chief Inspector Guy Guiana urged any witnesses or anyone with dashcam vision in the area at the time to come forward.

"While it's unfortunate that three vehicles were damaged, it was extremely lucky no one was injured in the incident," he said.

"Throwing rocks at oncoming traffic is a very serious matter and we are keen to speak to anyone with any information about this dangerous incident."

Anyone with information about this incident is urged to contact Crime Stoppers on 1800 333 000 or https://nsw.crimestoppers.com.au