GMP表示，這與 "在伯里其他地方以反社會方式使用煙花 "沒有關係，並呼籲任何知情者站出來。
Ch Insp Samantha Goldie說。"雖然我們預計會有抗議活動發生，並儘可能地為其提供便利，但我們絕對不能容忍暴力。
The FA Cup tie between Bury AFC and North Shields, which was shown live on the BBC, was paused following the incident which happened 20 minutes after kick-off on Saturday.
There have been recent demonstrations about the future of Bury AFC, which was set up in 2020 after Bury Football Club was expelled from the English Football League following financial problems.
It is not clear if the throwing of the flares was linked to these protests.
GMP said it was not connected to fireworks being used "in an anti-social manner elsewhere in Bury" and is appealing for anyone with information to come forward.
Ch Insp Samantha Goldie said: "While we anticipate protests taking place and facilitate them where possible, we absolutely do not tolerate violence.
"This is a public event and ultimately we want everyone to be safe and have an enjoyable time. Thankfully this reckless and dangerous action by a few did not result in serious injury."
Earlier this year, the number of arrests at football matches across the top five English leagues was reported to be at its highest levels in years, according to the UK's football policing lead.
Under the new rules, people who carry or use pyrotechnics or smoke bombs will be banned from matches, and those identified will be reported to the police.
The leagues and the FA say they will also ask the government to restrict the supply of the devices.