A leading British daily says South Korea’s chocolate-coated snack, Choco Pies, have become an unofficial currency at North Korea's Gaeseong Industrial Complex and are becoming a threat to the plant’s productivity.

According to The Telegraph, North Korean workers in the industrial park take home an average monthly wage of some 124-thousand won, but earn far more by selling the Choco Pies they receive from their South Korean employers.

The report noted that while Choco Pies, which are made by Orion Confectionery in South Korea, sell for around 300 won each in the South, they are considered a “much sought-after luxury in the impoverished North.”

The daily said that on the black market, one Choco Pie is reportedly sold for as much as ten dollars.

The report said that “inflation saw Choco Pie payments soar from two cakes a day to as many as ten, with companies that refused to match the pay rate after seeing their employees' productivity tumble.”