The 18-floor office tower that is home to The Inquirer, the Philadelphia Daily News, and Philly.com is inching closer to sale.

Philadelphia Media Network, owner of the two daily newspapers and the online portal, is reviewing an unspecified number of bids for the 526,000-square-foot building at 400 N. Broad St.

Mark Block, PMN's vice president for external affairs, said Thursday that a decision "based on the best offer" would come "sooner rather than later," most likely within a month.

"This has been a thoughtful and deliberative process," he said, adding that the building, erected in 1925 to house The Inquirer, had "attracted a lot of interest" from both commercial and residential developers.

"We're very pleased by the number of proposals," said Block, who didn't identify the bidders.

Real estate sources in Philadelphia contacted Thursday could not shed light on the identities of the bidders for the building, which was last put on the market in August 2007 by then-chief executive officer Brian P. Tierney and his ownership group, Philadelphia Media Holdings.

Patriot Equities L.P., of Wayne, had agreed in February 2008 to buy the property, which includes a five-level, 502-space parking garage at 15th and Callowhill Streets and an adjacent 200-space surface lot. But that sale never closed.

The building was valued at less than $30 million in October when the newspaper company changed ownership in bankruptcy bidding.

The company would not identify the prospective buyers. Philadelphia developers Bart Blatstein and Carl Dranoff are among those who have toured the building. Dranoff said he had looked at the site for residential development but declined to make an offer.

Block said a leaseback arrangement that would keep the two newsrooms, Philly.com, and the company's administrative office space in the building was being considered.

Each proposal is being reviewed by "a number of individuals," he said, which means that a decision will take time.

Nearly 750 journalists, advertising representatives, and other employees work in the building, which publisher and CEO Greg Osberg has described as "underutilized."

Some of that unused space results from the newspapers' moving the printing, bundling, and delivery processes to a new plant in Upper Merion Township in 1992.

Contact real estate writer Alan J. Heavens at 215-854-2472 or aheavens@phillynews.com.