Police are investigating after a flare was thrown into the disabled fans' section during Sunderland's football match with Birmingham City.
The object was thrown by away supporters who were seated in the stand above on Saturday.
Footage recorded by a fan shows what appears to be a flare land with a plume of blue smoke rising into the air.
It landed between the wheels of a wheelchair but no-one was injured, Northumbria Police said.
A spokesman said officers were trying to identify those responsible and the force asked anyone with information to get in touch.