A bus user was reportedly punched, and another threatened, whilst the vehicle was stationary in St Ives.
The incident took place at 10.00pm on May 21, when a Stagecoach bus had stopped on Ramsey Road.
Police have since released CCTV images of a woman they would like to speak to in connection with the alleged assault.
A spokesperson for Cambridgeshire Police said: "A man was punched and another person threatened on a Stagecoach bus while it was stationary at a bus stop in Ramsey Road, St Ives at about 10.00pm on May 21.
"Anyone with information should report to police online either at www.cambs.police.uk/report or via webchat and quote 35/35858/22."
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