Milan revealed on Twitter on Friday that they had acquired the Spaniard on a temporary basis until the end of the campaign, but there was no such confirmation from the Toffees.
At the time of writing, neither club had made a public statement on the status of the transfer.
Previously, reports have claimed that Milan's move for the Barcelona academy graduate had stalled due to the two clubs' failure to agree a loan fee.
Deulofeu has made just four Premier League starts for Everton this season having fallen out of favour under new manager Ronald Koeman.
GERARD DEULOFEU || AC MILAN || SKILLS + GOALS + HIGHLIGHTS 2017 pic.twitter.com/TJfHqkTXMj— #VogliamoMaldini (@HoldTheMilan) January 20, 2017
He joined the club on a permanent basis in the summer of 2015 after impressing while on loan from Barca during the 2013-14 campaign. In between, he was sent out on loan again by the Catalans to Sevilla.
Deulofeu was not included on the list of players in Milan's squad for their crunch league match against Napoli this weekend.
Vincenzo Montella's side, currently in fifth, will be just a point behind their third-placed rivals with a game in hand if they secure victory at San Siro on Saturday evening.