Nassau police arrested the owner of a store in Plainview Tuesday and seized more than $40 million worth of clothing in what authorities called the largest counterfeit clothing bust they have ever seen.

Detectives say they discovered an entire operation in the basement of Linny's Boutique, where clothing items were being stamped with high-end names. The items were fakes, police say, and were being sold online and in the store by owner Lindsay Castelli, of Smithtown.

The store contained thousands of knockoff Gucci, Louis Vuitton, Chanel, Prada and Dior clothing items that were being seal-pressed. Police say they also found 22 heat-pressing machines.

“A simple $10 sweatshirt – you put the Chanel brand on it, it sells for $5,300,” said Nassau Police Commissioner Patrick Ryder. “They would take a $3 hat…and sell [it] for $300.”

After receiving tips from sources, police conducted an 18-month investigation that involved surveillance and undercover purchases at the store. Police say a further investigation revealed that the items were also being sold on a website she was running and shipped to consumers.

Castelli surrendered herself to Nassau County Asset Forfeiture Detectives on Oct. 7.

Castelli was charged with trademark counterfeiting. She's due back in court Nov. 2. If convicted, she could face up to four years in jail.

News 12 went to Castelli’s home for comment, but there was no answer. Her neighbors also didn’t have any comments.

Carole Rutkovsky, of Plainview, says she bought some items at the store and feels “totally betrayed.”

Bonnie Furman, of Melville, says she paid $50 for a Chanel sweatshirt from the store and had a feeling it was a fake.

“It was never the kind of stuff that I would think was real. But it said Chanel…I never thought it was great quality,” she said.