Monday 20 February 2017 14:21, UK
Leicester City have contacted the FA to report their concerns about the behaviour of Millwall supporters at the New Den on Saturday.
The Foxes are expected to lodge an official complaint after receiving "numerous complaints relating to the constant abuse, provocation and intimidation of players, staff and supporters" during their FA Cup fifth-round defeat.
The Metropolitan Police confirmed at the weekend that three men were arrested after disorder at the final whistle.
Millwall say they are "extremely disappointed" the champions did not raise their concern on the day of the game.
Leicester's concerns with the FA are believed to relate to the following allegations:
A Leicester City spokesman said: "We have personally congratulated Millwall on a merited victory and wish them every success in the sixth round.
"However, following receipt of numerous complaints relating to the constant abuse, provocation and intimidation of our players, staff and supporters from our arrival at the stadium, throughout the match and its immediate aftermath, we have registered our dissatisfaction with the FA.
"We are awaiting the FA's response. The club accepts the defeat, but we simply will not accept the safety of our supporters, players and staff being compromised."
Millwall said: "We have been made aware of these allegations today and are extremely disappointed that Leicester City, as is the professional protocol in such instances, did not raise them on the day of the game itself.
"This morning we received an email from Leicester thanking Millwall Football Club for the hospitality extended to them so are surprised that these serious allegations, which should have been discussed on the day, have come to our attention in the manner they have."