The Halifax District Investigations Team would like to speak to anyone who saw a group of people fighting outside the Craft Bar on Stainland Road during the evening of Friday May 13, at about 22.40.
Officers attended, and following enquiries, later arrested two men aged 19 and 21 on suspicion of affray.
They have both been released under investigation.
It is believed several people who have not come forwards were assaulted in the fighting and police would like to speak to them or anyone else who can assist the enquiry.
Information can be given to the Halifax District Investigations Team on 101 referencing crime number 13220258889.
It can also be given online at www.westyorkshirepolice.uk/101livechat or anonymously to the independent Crimestopers charity on 0800 555 111.