More than two dozen bars in New Jersey have been deceiving patrons in a nasty way.

Yesterday, state officials announced that they had raided 63 bars in the state and collected liquor samples for testing as part of a yearlong investigation, “Operation Swill.” They launched the investigation in January after the Division of Alcoholic Beverage Control had received more complaints than usual about potentially mislabeled liquor. With the help of an informant with knowledge of the industry, undercover investigators collected the samples by ordering “neat” drinks—or drinks without ice or mixers—from the establishments and then covertly taking samples for testing.

According to officials, 29 New Jersey bars and restaurants, including 13 TGI Fridays, had been passing off fake or cheap booze as high-priced premium liquor. One establishment substituted rubbing alcohol dyed with caramel coloring for scotch; another refilled premium liquor bottles with dirty water.

New Jersey Attorney General Jeffrey Chiesa told the AP that the scheme was “a dishonest ruse to increase profits and is a slap in the face of the consumer.”

The establishments have seven days to turn over records that will help authorities determine how many patrons were overcharged and how much they overpaid.

The AP reports that TGI Fridays Inc. is conducting an internal investigation.

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