Leeds goalkeeper Casper Ankergren was subjected to taunts by the Millwall fans following the goal and also had missiles thrown at him, and Scotland Yard have confirmed that one man has been arrested on suspicion of assault.
The FA's decision to look into the incident comes on the back of the Danish goalkeeper's plea for action be taken against the London club.
Ankergen speaking after the game said: "There was something thrown at me, I didn't see what it was as I turned my back on it. It's very bad for football and Millwall should be punished. I was pushed in the back by one of the fans that came on the pitch too. It should never happen, fans should not be allowed on to the pitch.
When asked about the security at the game he continued: "I'm not sure what the security were doing as no-one came to remove them. They are meant to be here to protect the players, it's not good enough. Anything could have happened, luckily it didn't and hopefully I wouldn't experience that again. English fans are normally much better than Danish fans, who always throw stuff on the pitch and at players. But it's happened here at Millwall and I hope something will be done. It is a disgrace to football."
A touch of kettle and black there from Casper which would be confirmed by anybody whose been to Elland Road where the security does absolutely nothing to help away fans under
Anyway, Millwall have confirmed that any fans arrested will be banned from all their games for the foreseeable future and that Ankergren has received apologies from the club.