Seven people have been arrested after Nottingham Forest hosted their rivals Derby County at the City Ground.
The game took place midday on January 22nd and ended with the hosts winning 2-1.
Six people were arrested for public disorder offences and one for common assault on a police officer.
Police are investigating reports of a flare being thrown into the away side during the match.
Chief Inspector Neil Williams, match commander, of Nottinghamshire Police, said: “We are aware of an incident in which a flare is reported to have been thrown into the away section during the weekend’s match and are in the process of reviewing CCTV footage from the game.
“Nottinghamshire Police is currently working closely with both clubs to identify anyone who could have been involved and would ask anyone who has any information about what happened to get in touch with us.”