New research published in the journal Nature details findings that posit somewhere in East Asia is producing a banned ozone depleting chemical.

According to the BBC, CFC-11 was used in the 1930s as a refrigerant. It could also be found in solvents and aerosols. Scientists say the continued production of the chemical may slow the recovery of the Ozone.

Speaking to Time, university of Maryland expert Ross Salawitch said the "rogue production" of CFC-11 could hurt the ozone recovery.

Researchers considered several factors to explain the continued presence of CFC-11, but concluded that unreported new production is behind it.