Gareth Southgate has confirmed that Phil Foden and Mason Greenwood will not be selected for England's UEFA Nations League game in Denmark tomorrow.
The Three Lions manager was speaking from Reykjavik, where his side have been based since facing Iceland on Saturday.
In a statement, an FA spokesperson added: "While in Iceland, both Phil Foden and Mason Greenwood spent time outside of our private team area, which was a breach of our COVID-19 rules.
"While they did not leave the team hotel, it was an unacceptable breach of our protocol. They have both apologised for their serious lack of judgement.
"The FA will be launching a full investigation into the circumstances leading up to this breach. We have spoken to the Football Association of Iceland to offer our apologies for this incident and to ensure them that we are taking the appropriate steps.
"We have also assured the Danish Football Union that all other players and staff members have been isolated within our group throughout this period.
"Our immediate priority now is preparing the team for the match against Denmark tomorrow."
Updated England squad to face Denmark:
Tammy Abraham (Chelsea), Trent Alexander-Arnold (Liverpool), Conor Coady (Wolverhampton Wanderers), Eric Dier (Tottenham Hotspur), Joe Gomez (Liverpool), Jack Grealish (Aston Villa), Dean Henderson (Manchester United), Danny Ings (Southampton), Harry Kane (Tottenham Hotspur), Michael Keane (Everton), Ainsley Maitland-Niles (Arsenal), Tyrone Mings (Aston Villa), Mason Mount (Chelsea), Kalvin Phillips (Leeds United), Jordan Pickford (Everton), Nick Pope (Burnley), Declan Rice (West Ham United), Jadon Sancho (Borussia Dortmund), Raheem Sterling (Manchester City), Kieran Trippier (Atletico Madrid), James Ward-Prowse (Southampton)