By midday, shares of the Oakland, Calif., broadcaster were trading at $10.42, down $2.15 or 17 percent after touching a low of $9.95. Representatives of Apple, of Cupertino, Calif., declined comment on the reports.
Apple shares set an all-time record high of $682.48 in Friday trading.
Pandora already competes with music offerings from Apple's iStore. On the other hand, Apple allows customers to listen to Pandora services on the iPhone and Mac products.
Pandora has not reported any profit since its 2011 initial public offering and said it expects to report revenue ranging from $425 million to $432 million for the year, with an adjusted loss between 4 and 8 cents a share.