The Football Association is investigating an allegation of racial discrimination during Saturday's Championship game between Charlton Athletic and Leeds United.
It is understood the incident involved Leeds goalkeeper Kiko Casilla and Charlton forward Jonathan Leko.
Referee John Brooks is believed to have included the allegation in his match report after Charlton's 1-0 win.
The FA will now speak to both clubs and the players allegedly involved.
A statement from the Addicks said: "Charlton Athletic can confirm that an allegation of racial abuse directed at Jonathan Leko by an opposing player during Saturday's game against Leeds United was reported to referee John Brooks.
"The club will support Leko throughout the process and will not be making any further comment until the investigation is concluded."
Leeds said in a statement they were aware of the allegation and would be "working with the FA during their investigation".
Anti-discrimination campaign group Kick It Out said it would also offer its support to 20-year-old Leko.
Under rules introduced for the 2019-20 season, the minimum suspension for a player found guilty of an aggravated breach of the FA's discrimination rules will be six matches, which can be increased depending on any additional aggravating factors.