Argentine forward Lucas Alario has already undergone a medical with Bayer Leverkusen, according to local reports in Argentina. Those also suggest that the 24-year-old underwent his medical without the approval from River Plate.
In a letter addressed to Leverkusen CEO Michael Schade, the Argentine club are threatening legal action, who will refer to FIFA, according to Sport Bild.
It was reported by Kicker last week that Bayer Leverkusen were interested in signing Alario while their opening offer of €16m was rejected. If the deal is to go through, River Plate are expecting to receive around €25m.