The future of the Germany international has been the subject of much conjecture this season, with persistent reports claiming the Red Devils have made him an off-season target.
BVB head coach Jurgen Klopp, who will be stepping down from his role at the end of the campaign, revealed earlier this month that Hummels is “thinking things over” after a difficult year for Dortmund.
German weekly magazine Sport Bild reported on Wednesday that United have taken the first steps in acquiring the services of the 26-year-old centre-back by lodging a €30 million bid with their Bundesliga counterparts.
But Dortmund sporting director Michael Zorc was not forthcoming when quizzed about the reported offer, telling Bild: “I can’t confirm that.”
Meanwhile, Hummels added: “I don’t want to comment on it all the time. I’ve done that a few weeks ago, and that has to be enough.”