Talks are ongoing, a source said.
Comcast is interested in the same set of assets that Disney approached Fox about earlier this year, sources said. Also of interest to Comcast is acquiring the international assets of Fox, given that the Philadelphia-based company is heavily concentrated in the U.S.
CNBC reported last week, citing sources, that 21st Century Fox has been holding talks to sell most of the company to Disney, leaving only an entity focused on news and sports.
A Comcast-Fox deal would have the same regulatory issues that Disney would have in acquiring the Fox assets, the sources said.
Disney under U.S. rules could not own two broadcast networks. And that would be the same case with Comcast. Neither company is talking about purchasing all of Fox, sources told CNBC.
Any deal by Comcast or Disney would also likely exclude Fox's news and sports programming assets for fear of running foul of antitrust laws.
Fox shares jumped more than 6 percent in after-hours trading. Comcast shares rose about 0.75 percent, while Disney shares were mildly lower.
CNBC reported Friday that while the Disney and Fox talks were not ongoing, a deal was not totally dead.
Verizon Communications is also interested in acquiring parts of Fox, Dow Jones reported after the bell Thursday. A source told Reuters that Verizon is in the early stages of exploring a deal, which would provide content to stream to its mobile subscribers.
Disclosure: Comcast owns CNBC parent NBCUniversal.