Trading Standards officers say they raided a home in Kelty and seized £60,000 worth of suspected fake goods.
Police said five people were detained and released after questioning.
The goods included clothing, footwear, cosmetics, jewellery and electrical items.
Dawn Adamson, Trading Standards Service Manager said: “Acting on intelligence received, and regular monitoring of online selling sites, our officers have seen a growing trend in individuals using websites like Facebook and Gumtree to sell illicit goods.
“Our officers are extensively trained to investigate cyber-crime relating to counterfeit goods and do so in liaison with a wide network of partners involved in the fight against fakes.”
An investigation continues.