Sunderland supporters were stunned when a fan at the Stadium of Light pulled down his trousers and appeared to defecate in his seat, according to reports.
Pictures of the fan are circulating on social media - which Echo has decided not to publish - appear to show the man defecating while stunned supporters look on from their seats.
Reports from fans’ forums say the incident happened in the stadium ’s South Stand during the Black Cats’ 3-1 home loss to Reading yesterday.
Social media posts say the fan, who is believed to be a season ticket holder, was led away by police.
A spokesman for Sunderland AFC said: "We are aware that an incident took place.
"The matter is in the hands of Northumbria Police."
Northumbria Police were unable to confirm details of the incident.
One fan posted on the Ready To Go message board: "I seen everyone move away and there was just one ****** kid stood there ... coppers came n took him out."
Another fan wrote: "What sort of filthy animal even does something like this? He should be locked in a cage."
And a third added: "I don't think he knew what he was doing ... he looked genuinely confused as to why people were having a go at him. Right in front of the security box as well."