The United States has blocked imports of sea salt products from a major South Korean salt farm accused of using slave labor, becoming the first trade partner to take punitive action against a decadeslong problem on salt farms in remote islands off South Korea’s southwest coast.

U.S. Customs and Border Protection issued a withhold release order against the Taepyung salt farm, saying information “reasonably indicates” the use of forced labor at the company in the island county of Sinan, where most of South Korea’s sea salt products are made.

Under the order issued last Wednesday, Customs personnel at all U.S. ports of entry are required to hold sea salt products sourced from the farm.

Taepyung is South Korea’s largest salt farm, producing about 16,000 tons of salt annually, which accounts for approximately 6% of the country’s total output, according to government data, and is a major supplier to South Korean food companies. The farm, located on Jeungdo island in Sinan and leasing most of its salt fields to tenants, has been repeatedly accused of using forced labor, including in 2014 and 2021.

South Korean officials stated that this was the first time a foreign government had suspended imports from a South Korean company due to concerns over forced labor.

In a statement to The Associated Press on Monday, South Korea’s Foreign Ministry said relevant government agencies, including the Ministry of Oceans and Fisheries, have been taking steps to address labor practices at Taepyung since 2021. While not providing direct evidence, it said it assesses that none of the salt produced there now is sourced from forced labor. The ministry said it plans to “actively engage” in discussions with the U.S. officials over the matter.

The fisheries ministry said it plans to promptly review the necessary measures to seek the lifting of the U.S. order. The widespread slavery at Sinan’s salt farms was exposed in 2014 when dozens of slavery victims — most of them with disabilities — were rescued from the islands following an investigation by mainland police. Some of their stories were documented by The Associated Press, which highlighted how slavery persisted despite the exposure.

U.S. Customs said it identified several signs of forced labor during its investigation of Taepyung, including “abuse of vulnerability, deception, restriction of movement, retention of identity documents, abusive living and working conditions, intimidation and threats, physical violence, debt bondage, withholding of wages, and excessive overtime.”

Lawyer Choi Jung Kyu, part of a group of attorneys and activists who petitioned U.S. Customs to take action against Taepyung and other South Korean salt farms in 2022, expressed hope that the U.S. ban would increase pressure on South Korea to take more effective steps to eliminate the slavery.