Apple spokeswoman Jennifer Bowcock said she did not know about Jobs' attendance, which Bloomberg also reported on Wednesday.
Apple's shares crept up on Wednesday to their highest level since August 28, 2008, ahead of the widely watched event at which the company was expected to unveil a new line of iPods for the crucial holiday selling season.
If charismatic showman Jobs, who traditionally orchestrates Apple's media showcases, takes center stage, he will be making his first public appearance after returning from medical leave in June.
Analysts expect Apple to announce iPods with digital cameras. Few were expecting game-changing product announcements.
The company's shares touched a high of $174 before slipping to stand 0.4 percent higher at $173.65 around noon.
(Reporting by Edwin Chan, editing by Maureen Bavdek)