Police announced on Saturday that they are investigating claims of racist abuse after Manchester City's Aleksandar Kolarov became involved in a row with a supporter at St James' Park.
Northumbria Police said they had received a complaint after City's 3-1 win over Newcastle United in the Premier League.
"Northumbria Police has received a report of racist language having been used at the St James' Park stadium during the Newcastle United v Manchester City match today (Saturday)," said a police spokesman.
"Northumbria Police takes such allegations extremely seriously and inquiries are ongoing into the incident."
Reports said Kolarov, a 27-year-old Serbian international left-back, got involved in a heated exchange with a spectator brandishing an Albania flag as he warmed up by the side of the pitch.
There is a long history of tension between Serbia and Albania, particularly with regard to the disputed Kosovo region.
Neither City nor Newcastle were prepared to comment on the incident.
Kolarov came on as 37th-minute substitute for injured City midfielder Samir Nasri but was then taken off with 18 minutes to play.