CCTV images have been released of men detectives want to speak to about an attack in Doncaster town centre.
It is believed the men could hold vital information about an incident in Silver Street last month in which a 25-year-old man suffered serious injuries.
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He was set upon at around 11.30pm on Friday, April 13 and needed hospital treatment.
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A 29-year-old man arrested on suspicion of causing grievous bodily harm in connection to the incident has since been released under investigation.
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A South Yorkshire Police spokesman said: "Detectives have been pursuing a number of lines of enquiry in relation to the investigation and have now released images of two men who they believe may be able to assist with these enquiries.
"Do you recognise these men? Were you in the area at the time of the incident?"
Anyone with information should call South Yorkshire Police on 101 and quote incident number 1,190 of April 13.
Information can also be passed on via Crimestoppers on 0800 555 111.