Leicester City boss Brendan Rodgers said he is "bitterly disappointed" after three of the club's players breached Covid-19 protocols ahead of Leicester's 3-2 defeat to West Ham on Sunday.
Leicester are investigating three players for the breach of protocols, Sky Sports News has been told.
James Maddison, Hamza Choudhury and Ayoze Perez were all left out for the crucial clash by Rodgers.
Leicester lost the game 3-2 at the London Stadium to see their lead in third place cut to just a point with seven matches left this season, with Rodgers explaining after the game he had no choice but to drop the trio.
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Rodgers would not confirm the identity of the players involved in the breach, but said: "It was a decision I made, we had an internal situation last weekend and it is not a standard that we would expect.
"All those boys that you mentioned, they are all good guys, they are all good lads, but we have a standard on and off the pitch that we need to ensure we adhere and that is why the team has been developing well over these last couple of years."
Rodgers later confirmed, however, that the players involved would all return to the squad for Leicester's FA Cup semi-final with Southampton at Wembley next Sunday evening.
Rodgers continued: "But the boys will re-join this group after this game, the consequence of this behaviour is they will miss this game, but they will join the group next week and then we will get ready for a semi-final.
"It is internal and something that is being dealt with from within.
"The boys that you mentioned, it is something that of course is disappointing but I know them, it is a behaviour and a mistake that they have made, it is not their identity and it is certainly not the identity of what we are trying to produce.
"It would have been easy to just have them here, but it is not what we are about, we have a set of values for this team and this football club, and we have to adhere to that and like I say, the players in the main have been brilliant during my time, and they are top players.
"But they will re-join the group next week and they will work hard and we will all be back together again.
"You can do it if you are soft, but for me, it is always about discipline, in order to be a winner and to compete at the top end of this table, you have to act like a winner and that winning and that winning mentality is a certain level of behaviour and a mindset that allows you to prepare every day for every game.
"From a personal perspective I was bitterly disappointed. But it's a mistake that they've made and I won't hold it against them. It's in the past now.
"So no, I had no hesitation, you can fine players nowadays and whatever else, but it is a drop in the ocean the consequence what was the football game today, unfortunately we did not have them.
"But we will move on from it and look to finish the season stronger."
Leicester say the players involved have apologised for their behaviour and the club will investigate the matter internally.
A club statement said: "It is extremely disappointing to learn of a breach that had the potential to undermine the efforts of club staff to protect the environments in which our teams train and play.
"Appropriate measures have been taken to prevent our team bubbles being compromised.
"We wholly expect our people to behave in a way that reflects the national effort and the sacrifices made by our communities to control the spread of the virus. Those involved have apologised for their poor judgement.
"Our response to the matter will be concluded internally."
Maddison has been an integral member of Rodgers' squad this season, scoring 11 goals and providing 10 assists in all competitions despite spells out with injury.
Perez, who has provided three goals in 27 appearances, and Choudhury, who has scored once in 20 games, were also regular started under Rogers this campaign.