North Yorkshire Police are appealing for witnesses after "significant disorder" broke out during the 1 April 2015 Evo-Stik Northern Premier League clash between Whitby Town and FC United of Manchester.
The trouble was mainly caused by home supporters, who threw flares onto the pitch at The Turnbull Ground. The pyrotechnics were also thrown into the crowd, police said.
Officers believe that the flares were hidden inside the ground at some point before the match. An 18-year-old local man was arrested in connection with the disorder and police are working to identify other people who were involved.
Anyone who was at the match and witnessed the disorder is urged to contact North Yorkshire Police with information. In particular, officers would like to hear from anyone who filmed or took photos of the disorder.
Footage should be sent to firstname.lastname@example.org
FC United of Manchester, which was formed in the wake of Manchester United's 2005 takeover by the Glazer family, won the match 4-0.