Australia batsman David Warner was dropped for the country's Champions Trophy match against New Zealand yesterday, amid complaints from Ashes rivals England of an "unprovoked physical attack" on their player Joe Root.
Warner "was allegedly involved in a physical altercation with an England player in the early hours of Sunday morning following the Champions Trophy match between the teams in Birmingham", Cricket Australia said.
The England and Wales Cricket Board (ECB) also said Warner had initiated an "unprovoked physical attack on a member of the England team" in a Birmingham bar following England's 48-run victory over Australia at Edgbaston on Saturday.
It added: "Warner has admitted behaving inappropriately and has since apologised to the player involved who has accepted the apology.
"Following a full investigation the England team management has concluded that the England player was in no way responsible for nor retaliated to the attack.
"The ECB has concluded that this is a matter for Cricket Australia and has no further comment to make."
England captain Alastair Cook later confirmed the identity of the player involved as Yorkshire batsman Root while speaking at a London news conference ahead of the team's group match against Sri Lanka at The Oval today.
"Joe seems fine," Cook said. "It's unfortunate this has happened and he wants to put it behind him. After investigating it from our side, we don't believe we have done anything wrong.
"It's a shame it has happened, in some way it has marred what was a very good win for us.
"Our conduct in the England team is vitally important. We are aware of our position and responsibilities."
Sky TV quoted the manager of the Australian theme bar Walkabout in Birmingham's entertainment district, where the incident took place, as saying there was a "small altercation", but that all the players got on well afterwards, with Warner picking up the bar tab.
Warner last month came under fire for a Twitter tirade directed at two respected Australian cricketing journalists after a story about corruption and fixing in the Indian Premier League was illustrated with a picture of him.