As The Observer reported online this week, Rupert Murdoch’s News Corporation has joined Mr. Ross’ Related Companies in its bid for the right to develop the rail yards, a source familiar with the bid said.

If Related won the bid, News Corp. would move from its headquarters at 1211 Avenue of the Americas into a new tower built over the rail yards, the source said. Last week, The Observer reported that Condé Nast would leave 4 Times Square for a new, 1.5-million-square-foot tower if Mr. Durst and Mr. Roth’s Vornado won a bid; and it was also reported that Morgan Stanley had teamed up with Tishman Speyer.

The source said that it could take months to select a bid winner, but that the yards’ owner, the Metropolitan Transportation Authority, considered Related, Vornado-Durst and Tishman Speyer the front-runners. The source said that Brookfield Properties’ bid was also being taken seriously, even though it goes without a major tenant, and that Mr. Barnett’s Extell Development had, at first look, the least formidable bid. All the developers’ bids were given to the M.T.A. on Oct. 11.

The possibility that News Corp., which controls the naming rights to its tower at 1211 Avenue of the Americas, would relocate all but assures that the city will have a high-wattage tenant in the West 30’s, near 11th Avenue, by 2015.

A spokesman for News Corp. would not comment.