CCTV images have been released of football fans wanted over a clash between Sheffield United and Grimsby Town supporters.
Disorder broke out after the pre-season friendly between the teams in Grimsby on July 23.
Officers from Humberside Police have issued 10 images of men, believed to be a mix of Blades and Grimsby fans, who they believe may hold vital information about the incident.
Since the trouble, nine men, aged between 18 and 35, have been arrested on suspicion of violent disorder, along with two youths aged 14 and 17.
All have been released on police bail, pending further inquiries.
As violence flared, a police officer suffered a head and ankle injury after bottles were hurled at him.
Shocked holidaymakers, some with children, fled as fans began throwing bottles and had running battles with baton-wielding police officers.
At the time Humberside Police warned that the force would 'come down hard on offenders' and seek football banning orders for those involved.
Match commander, Superintendent David Hall, said at the time: “Quite frankly this sort of behaviour is not acceptable and will not be tolerated."
"Football matches should be friendly sporting events that families can attend and enjoy. We will not allow the minority of people to spoil such occasions."
Anyone with information should call Humberside Police on 101 or Crimestoppers on 0800 555111.
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