Police were called to a report of an altercation at The Dubliners pub on Bridge Street in Thornaby at around 9.30pm on Sunday (August 30).
A 22-year-old man suffered serious facial injuries and he remains at James Cook University Hospital whilst receiving treatment.
Enquiries are ongoing and detectives are appealing to speak to anyone who may have witnessed what happened.
Anyone who may have information regarding the incident is asked to contact Detective Sergeant Lyndsey Dale from Stockton CID on the non-emergency number 101, quoting incident number 141842.
Independent charity Crimestoppers can be contacted anonymously on 0800 555 111, or online at www.crimestoppers-uk.org.
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