Cops acting on a tip tackled a labyrinth of secret tunnels, trapdoors and fake brick walls to uncover an immense cache of counterfeit luxury goods in a Chinatown building, officials said yesterday.

The raid on Broadway between Canal and Howard streets yielded knockoffs of high-end watches, handbags, wallets and sunglasses with an estimated retail value of $125 million, said Lt. Mark Magrone, commander of the Staten Island Intelligence Bureau.

He said the stash of fakes is the largest uncovered in recent history.

Ten people were arrested during the Wednesday raid.

"They took immense security measures to prevent anyone from entering the building," Magrone noted.

He said Staten Island, Chinatown and Emergency Service Unit cops raided the warehouse at 3 p.m. and spent hours breaking through heavy bolts, locks and gates wending their way through secret tunnels and trapdoors to find the loot.

The highest-quality knockoffs were found in a large vault. The rest of the illegal stash was discovered in the maze of hidden tunnels.

Among the phony trademarks found on the illegal wares were Rolex, Movado, Gucci, Prada, Cartier and Tag Heuer.

Some of the replica watches were so well made, with movements that duplicated Swiss movements, that it was difficult to tell they were fakes.

Magrone said a three-month investigation that started with a tip on Staten Island led them to the building and the booty.

He refused to provide details about where the knockoffs had been produced, how they had gotten to New York, and where they were going to be sold, noting that "the investigation is ongoing."

He also would not provide any background information about the 10 people arrested.

The eight men and two women - who were hit with felony charges of first-degree trademark counterfeiting - were identified as David Tran, 33; Lau Tran, 24; Ngan Tran, 19; Guo Pan, 46; Mahamed Diawara, 38; Hunt Chent, 50; Whenkai Chen, 55; Mahabov G. Boulingu, 27; Zhong Jiang, 44; and Mamadou Sow, 35.

Most counterfeit watches come to the United States by way of Hong Kong, according to Jack Pfeifer, a senior U.S. Customs inspector based at Kennedy Airport.

He said China generally supplies the bulk of the material and parts, with most of the work and watch assembly performed in Hong Kong.

Then the goods are flown to major ports of entry in the United States.

"The better-quality watches come as component parts and are assembled at domestic factories so we can't catch them coming in," he said.

"They apply the trademarks after they come in."

FAKE SHAKEDOWN

The trademarks on the watches, sunglasses, handbags, wallets and other merchandise that police found stashed in a Chinatown warehouse were pretty impressive - they included Rolex, Movado, Gucci, Prada, Cartier and Tag Heuer. But they were all knock-offs. If sold on the street or on-line at the retail price of the genuine goods, they could have meant $125 million in sales for the counterfeiters and their cronies, industry experts told police.

Route of the Rip-Offs

Here's how counterfeit luxury watches get to the streets of New York.

China: Bulk of the watch parts are manufactured

Hong Kong: Most of work and assembly is done

New York: Assembly is finished, trademark is applied; watches are wholesaled to street vendors, flea markets, Internet auction sites and others