Twentieth Century-Fox says there is a possibility that some of its employes and the company itself may be indicted or held in contempt in connection with a federal grand jury investigation in New York into possible antitrust violations by the movie giant.

The disclosure, made in a filing with the Securities and Exchange Commission yesterday, marks the first indication from the firm of the possible results of the probe.

The grand jury has been reviewing evidence on allegations that Fox employes illegally forced theater owners to show the largely unsuccessful movie, "The Other Side of Midnight," if they also wanted to screen the box office hit, "Star Wars." Such a practice would violate federal antitrust laws and a 1951 consent agreement Fox signed promising not to use such practices.

The disclosure was made in Fox's registration statement for an offering of $50 million of subordinated debentures due in 1998.

The filing recounted Fox's huge earnings increase in 1977, due "for the most part to the unprecedented success of the motion picture "Star Wars," which generated approximately $130 million of the company's total $321.5 million in film rentals."

But the company also disclosed that it is a defendant in "numerous actions brought under federal or state antitrust laws by private plaintiffs."

These actions have been brought by some motion picture exhibitors and "a group of composers and lyricists," who, according to the filing, are seeking $100 million in damages (before trebling.)

The filing reveals other legal proceedings pending against Fox "involving alleged breach of contract, antitrust, tort or other miscellaneous causes of action arising from the business of the company."

Reached in Los Angeles by telephone, Twentieth Century-Fox spokesman Phil Meyers would not comment on the SEC documents. "We are not going beyond anything in the filing," he said.