AC Milan said they had signed Gerard Deulofeu on loan from Everton, but the Premier League club reportedly do not believe any deal is complete.
Milan announced the signing on their Twitter account on Friday, before multiple reports said Everton officials were furious at the Italian side's premature announcement.
And soon afterward, Milan deleted their initial tweet welcoming the 22-year-old to the club. They had yet to post the news on their website.
The two clubs have held extended talks, with Milan resisting a deal that would include an obligation to buy the 22-year-old on a permanent basis at the end of the season.
Everton manager Ronald Koeman said on Thursday that he would not stand in Deulofeu's way after freezing out the player in recent weeks.
At Milan, Deulofeu would reunite with fellow Spaniard Suso, with whom he won the UEFA European Under-19 Championship in 2012.
The winger has been in and out of the Everton side since joining on a permanent basis in summer 2015, following a previous successful loan spell in 2013-14, and has made 46 appearances since arriving from Barcelona.
However, he has struggled for game-time this season, with Koeman admitting he may need to leave for more regular action.
The Everton manager said on Thursday: "I spoke to Gerry and it's a difficult situation for the player. If he finds a solution to go and to play and to get game-time then it's not a problem.
"You have to always look for first what's the best for the club and second what is the best for the player, and for Gerry the best is that he gets game-time somewhere."