Officers in Worcester are appealing for witnesses to contact them as they continue an investigation into a reported assault on Monday 13 November.
The incident is reported to have happened on the number 35 bus near Cranham Drive at around 5.20pm, when a man in his 20s was punched in the face by another man.
The offender is then believed to have left with a woman and boarded another number 35 bus heading back towards town.
Investigations have identified a number of witnesses who were on the bus and police are appealing for them to make contact with investigating officer PC 21000 Hines by calling 101, quoting incident number 632s of 13 November.
You can also give information anonymously to the independent charity Crimestoppers. Phone Crimestoppers on 0800 555 111 or go online to crimestoppers-uk.org.