Ipswich Town said it is investigating after a Maidstone United fan appeared to fall from a stand on to spectators below.
The man was among away supporters in the upper tier of the Cobbold Stand at Portman Road for his team's 2-1 FA Cup win.
During first half goal celebrations, the fan appeared to roll down the roof and fall into the tier below.
It is understood no one was seriously injured during the incident.
"The club is aware of an incident involving a Maidstone United supporter in the Cobbold Stand at Portman Road during today's Emirates FA Cup fourth-round fixture," Ipswich Town said in a statement.
"The Club is investigating the issue thoroughly."
Suffolk Police has been approached for comment.
The National League South side pulled off an FA Cup shock by knocking the Championship high-flyers out of the competition.