More than 300 South Korean workers detained during a large immigration raid at a Hyundai electric vehicle plant in Georgia will be released and returned to South Korea, Seoul’s presidential chief of staff said Sunday, following negotiations with U.S. authorities.

Presidential chief of staff Kang Hoon-sik said South Korea and the United States had finalized arrangements for the workers’ release and that Seoul planned to send a charter plane once remaining administrative steps were completed. South Korea’s foreign minister, Cho Hyun, earlier said more than 300 South Korean nationals were among those detained in the operation.

U.S. immigration authorities said Friday that 475 people were detained when hundreds of federal agents raided the sprawling Hyundai manufacturing site in Ellabell, Georgia. Most of those detained were South Korean nationals, officials said. Many of the people taken into custody were transported to an immigration detention center in Folkston, Georgia, near the Florida state line.

Steven Schrank, the lead Georgia agent for Homeland Security Investigations, told reporters at a news conference that none of the detainees had been charged with any crimes and that the investigation remained ongoing. Video released by U.S. Immigration and Customs Enforcement showed a caravan of vehicles arriving at the site and federal agents directing workers to line up outside. The footage also showed several detainees being frisked and placed in restraints.

Video still from U.S. immigration authorities showing the operation at the plant

The operation targeted a Hyundai Motor Group facility that is still under construction and where the automaker and LG Energy Solution have partnered to produce batteries for electric vehicles. Georgia state officials have described the project as among the state’s largest economic development undertakings.

Seoul, a close U.S. ally, expressed "concern and regret" over the raid and dispatched diplomats to the site, officials said. South Korean government officials said they had engaged U.S. counterparts to secure the prompt release and repatriation of their citizens.

U.S. officials framed the action as part of ongoing immigration enforcement. Officials have not publicly disclosed the specific immigration violations being investigated, and Schrank emphasized that the inquiry was continuing. Media reports and released footage indicated that a significant number of federal agents participated in the operation.

The raid drew attention because of its size and because it focused on a high-profile manufacturing site that had been billed as a major job creator in the region. Advocates and politicians in both countries are likely to scrutinize the handling of detainees and the coordination between U.S. authorities and the South Korean government as repatriation plans proceed.

South Korea’s immediate next steps include finalizing administrative arrangements for travel documents and coordinating logistics for a charter flight to transport the workers home, Kang said. U.S. officials have said detained individuals will remain in custody while the investigation continues and until appropriate administrative or legal processes are completed.

Authorities from both countries said they would continue to exchange information as the case develops. The probe’s outcome could include administrative immigration actions; officials have reiterated that no criminal charges had been filed as of the most recent briefings.