An altercation involving four men left one in hospital with serious head injuries.
The incident happened at The Terrace bar on Fossgate at around at around 3.30am to 4am on Sunday 23 February.
Police say it involved the door supervisors and four members of the public who were all men.
Two of the men were hurt. One suffered serious head injuries which required hospital treatment.
A North Yorkshire Police spokesman said: “We are requesting the public’s assistance to help establish the full circumstances surrounding the incident.”
Anyone with information that could assist the investigation should contact North Yorkshire Police, details below.
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