A man was left with a serious facial injury after intervening in a fight in Huddersfield town centre during the early hours of this morning.
Police said the 33-year-old had tried to put a stop to an altercation taking place in Kirkgate, opposite the junction of Cross Church Street, between 4am and 4.30am.
He was taken to hospital for treatment along with a 44-year-old man also involved in the incident.
A West Yorkshire Police spokesman said: "Officers are particularly interested in speaking to a teenage male described as black, around 5ft 5in, with short black hair and a thin moustache.
"He was wearing a light grey matching tracksuit with stripes down the arms."
Officers arriving at the scene encountered a further incident during which a 34-year-old man was arrested on suspicion of affray and possession of a class B drug.
Any witnesses or anyone with information concerning the teenager described is asked to call PC Amy Lane at Kirklees CID via the non-emergency number 101 or use the online Live Chat facility on the force website.
Information can also be passed on anonymously via the independent charity Crimestoppers on 0800 555 111.