A West Ham fan lost a finger in the away end at Genk celebrating his side's second goal in their 2-2 Europa League draw.
Footage was circulating on social media on Thursday night showing the finger being picked up off the floor by a steward and placed on the fence in front of the travelling support.
Other supporters then tried to hurry the stewards at the game in Belgium to get ice and were frustrated at the lack of urgency.
It is understood the supporter, who will remain unidentified, lost his finger while banging the fence.