Philadelphia- from www.philly.com – A NATIONAL PORN conglomerate based in Center City was raided by the FBI, the IRS and local authorities early yesterday, but federal officials remain tight-lipped about what exactly they were seeking.

The feds, carrying search warrants, descended on the corporate offices of National A-1 Advertising, on 7th Street near Chestnut, about 9 a.m., reported AVN.com, an adult-entertainment trade magazine.

FBI agents refused to show the search warrants to managers on site and detained about 120 employees, said James Cybert, director of marketing for Hotmovies. com, a subsidiary of National A-1, according to AVN.com. Almost all of the employees left shortly before noon, but they were unaware why the agents had entered their second-floor offices, Cybert said.

“Nothing like having 100+ federal agents in your office. :(,” read a Twitter post from the National A-1 subsidiary, @HotMovies, posted around noon yesterday.

During the afternoon and into the evening, a steady stream of city police, state troopers, IRS agents and representatives of the U.S. Attorney’s Office entered and left the Washington Square building.

Agents drove up a U-Haul truck about 5:40 p.m., but it sat empty in the front of the building until 8 p.m.

Then authorities formed a line from the building, stocking the truck with boxes categorized by item number or by floor.

One young woman was denied entry into the building in the afternoon and began answering reporters’ questions.

She said she worked for National A-1 as a phone operator, but while she talked, a woman who claimed not to work for the company whisked her away. The woman then refused to talk about her job.

Besides the porn business, National A-1 also owns and manages National Watch & Diamond, on 8th Street near Chestnut, near Jewelers’ Row. A store employee confirmed the establishment was owned by National A-1’s chief executive, Richard Cohen, but declined to comment further.

But the bulk of National A-1 business is S-E-X.

The company owns or operates “Talk Line,” a phone-sex line; www.Escorts.com; www.GayMovies.com, and a host of “video on demand” porn sites. All the porn and sexy talk one could desire, within earshot of the Liberty Bell and above Stephen Starr’s hip eatery Jones.

The sites were inaccessible for most of the day, but for porn aficionados, there was a happy ending – the sites were back up last night.

FBI Special Agent J.J. Klaver declined to comment on the search and would confirm only that agents were at the location.

Patty Hartman, a spokeswoman for the U.S. Attorney’s Office, said the office “does not confirm or deny the existence or nonexistence of investigations.”

A CBS3 report stated the feds’ search was related to prostitution, possibly in connection to the company’s escorts.com site.

But one California-based porn colleague isn’t buying it.

Northeast Philly native Paul Fishbein, founder of AVN Media, has visited the National A-1 offices and said it “looks like Silicon Valley in there.”

“I certainly saw no prostitution there,” he said.

Fishbein, a George Washington High graduate, said he spoke with Cohen late yesterday afternoon while the mogul was still inside the corporate offices. Cohen, who rarely gives interviews, told Fishbein that he’d call him back today just to talk.

“This [type of raid] happens in obscenity cases,” Fishbein said. After covering the adult-entertainment business for 28 years, he said, “I know the pattern. They are going after a big name [within the adult-entertainment industry].”

Cohen has advertised with AVM over the years, said Fishbein, who called him “a good customer and friend.”

Cohen, Fishbein said, “pays his taxes, and he’s good about protecting kids from getting on the sites.”

“The good guy gets visited by the FBI,” he said.