Neil Lennon has made Pukki a top target as he looks to bolster his attacking options before the summer transfer window closes.
It was suggested that an injury to Klaas-Jan Huntelaar could scupper his plans, with Schalke reluctant to leave themselves short in an important area of the field.
It would, however, appear as though a deal is not dead.
Schalke are playing their cards close to their chest, but concede that Celtic are still looking to put a deal in place for a 23-year-old striker who is under contract in Germany until 2014.
Heldt told Sky Deutschland: "Celtic FC are interested in signing Teemu Pukki. I can confirm this.
"Teemu has a contract at our club and he is a Schalke player. At the moment, I am unable to confirm anything else."