The Belgian has not made a Premier League appearance since September and the German club's general manager insists several clubs are monitoring the Chelsea midfielder
The 22-year-old has struggled to cement a regular first-team place under Jose Mourinho this term and has not featured in the Premier League since September 21.
The Belgium international, who was criticised for his performances earlier this season by Mourinho, has been linked with a loan move in January and Heldt admits Schalke are among the clubs interested in securing a deal.
"There are numerous clubs, in Germany too, that are dealing with De Bruyne and who can imagine this,” Heldt told Sky Germany.
“In the end it is down to the player and the club. And the clocks are ticking there a little differently [at Chelsea].
“The bosses at the club decide what will happen. Kevin de Bruyne has to take his decision wether he wants do do something in January, too.
“All of this is speculation. The only thing I can tell you, is that lots of clubs are monitoring him."