Norwich City have banned three fans from home and away games following an incident during their win at Millwall.
The trio - one of whom was identified as throwing a pyrotechnic onto the pitch following Norwich's second goal - were arrested by police.
The Football Association has begun an investigation into the behaviour of Canaries supporters.
A club statement said it could result in a "substantial fine" or restrictions on fans attending future fixtures.
The statement continued: "The club would like to remind its supporters of the zero-tolerance policy on the use of flares, smoke bombs, fireworks or any other form of pyrotechnic inside stadiums.