The police watchdog has been asked to investigate how a 16-year-old was hit over the head with a baton as trouble flared after a football match.
A witness – who filmed the flashpoint following Barnsley's match against local rivals Sheffield Wednesday and shared it on social media– said the youth could have been killed.
South Yorkshire Police has referred the matter to the Independent Office for Police Conduct(IOPC).
Assistant Chief Constable Lauren Poultney said: "We understand the public will have concerns about the content of a video circulating on social media, with a 16-year-old suffering injuries to his head.
"South Yorkshire Police has referred this matter to the Independent Office for Police Conduct and we are waiting for their decision as to how this is progressed."
She said part of the investigation will go into wider disorder following the game on Saturday.
"The clip circulating on social media shows only a very brief period of time, and in order to understand the full context of the situation, we would ask anyone who was a witness or has further footage of what took place to contact us," she said.
Before the force made the announcement, shadow policing minister, Sheffield Heeley MP Louise Haigh, said: "This video and incident has understandably caused deep public concern in Sheffield and the wider area, and a referral should be made to the IOPC."
Spencer White, who filmed the incident, said there had been trouble between the two sets of fans after the match, as they both travelled towards the town's transport interchange.
The Barnsley fan said: "There were fights popping off randomly. Every two or three minutes there was a crowd of people getting rowdy.
"As I got to the train station there were two lads fighting, one a Barnsley fan and one a Sheffield Wednesday fan.
"I pulled out my phone to record it and the video shows the rest."
His film shows a 16-year-old fan being hit on the head with a baton, then struggle on the floor, with blood coming out of his head.
Witnesses remonstrated angrily with officers at the scene.
White, also 16, said: "He could have been killed, really."
