TRENTON, N.J. (CBSNewYork/AP) — Twenty-nine bars and restaurants – nearly half of them TGI Fridays – are in trouble with the State of New Jersey for allegedly filling top-shelf liquor bottles with lower-quality spirits and fooling customers.

As 1010 WINS’ Holli Haerr reported Wednesday, a yearlong investigation by the state Division of Alcoholic Beverage Control, dubbed “Operation Swill,” found that the establishments had swapped out the good liquor in an effort to fool customers and increase profits. The customer paid for the premium brand, but was instead, unbeknownst to the customer, poured the non-premium brand.

The enforcement action was executed by more than 100 state investigators. It stems from citizen complaints, confidential informants, and new technology used to test samples taken covertly from the establishments.