Kyle Lafferty has been withdrawn from the Northern Ireland squad ahead of the upcoming UEFA Nations League games against Kosovo and Greece.
Kilmarnock are investigating the alleged use of sectarian language by striker Lafferty.
A video circulating online shows the 35-year-old posing with a fan before allegedly making a sectarian comment.
Kilmarnock have now confirmed they are investigating the incident.
An IFA statement read: "The Irish Football Association is aware of a social media video which has been circulated widely. The association also notes an investigation has been launched into the video by the striker's club Kilmarnock."
A minor back problem has prevented Lafferty from participating in training since Tuesday.
In a statement, the Rugby Park club said: "Kilmarnock Football Club are aware of a video circulating online which appears to show a member of our playing staff using language of a sectarian nature.
"The club finds all forms of discriminatory behaviour completely unacceptable. The matter will be investigated by the club."
Baraclough: Still a route back for Lafferty
Ian Baraclough has insisted there is still a route back into international football for Lafferty despite his withdrawal from the team.
The Northern Ireland manager said a back injury had also been considered when the decision was made to withdraw the striker from the squad.
"It's not necessarily the end," Baraclough said. "It will be reported in some quarters as that and it will be sensationalised but I'm there for Kyle."