Kang Hoon-sik, chief of staff for President Lee Jae Myung, said that South Korea and the U.S. had finalized negotiations on the workers’ release. He said South Korea plans to send a charter plane to bring the workers home as soon as remaining administrative steps are completed.

Foreign Minister Cho Hyun is to leave for the U.S. on Monday for talks related to the workers’ releases, South Korean media reported.

U.S. immigration authorities said Friday they detained 475 people, most of them South Korean nationals, when hundreds of federal agents raided Hyundai’s sprawling manufacturing site in Georgia where the Korean automaker makes electric vehicles. Agents focused on a plant that is still under construction at which Hyundai has partnered with LG Energy Solution to produce batteries that power EVs.

Cho said that more than 300 South Koreans were among the detained.

The operation was the latest in a long line of workplace raids conducted as part of the Trump administration’s mass deportation agenda. But the one on Thursday is especially distinct because of its large size and the fact that state officials have long called the targeted site Georgia’s largest economic development project.

The raid stunned many in South Korea because the country is a key U.S. ally. It agreed in July to purchase $100 billion in U.S. energy and make a $350 billion investment in the U.S. in return for the U.S lowering tariff rates. About two weeks ago, U.S. President Donald Trump and Lee held their first meeting in Washington.

Lee said the rights of South Korean nationals and economic activities of South Korean companies must not be unfairly infringed upon during U.S. law enforcement procedures. South Korea’s Foreign Ministry separately issued a statement to express “concern and regret” over the case and sent diplomats to the site.

Video released by U.S. Immigration and Customs Enforcement on Saturday showed a caravan of vehicles driving up to the site and then federal agents directing workers to line up outside. Some detainees were ordered to put their hands up against a bus as they were frisked and then shackled around their hands, ankles and waist.

Most of the people detained were taken to an immigration detention center in Folkston, Georgia, near the Florida state line. None has been charged with any crimes yet, Steven Schrank, the lead Georgia agent of Homeland Security Investigations, said during a news conference Friday, adding that the investigation was ongoing.

He said that some of the detained workers had illegally crossed the U.S. border, while others had entered the country legally but had expired visas or had entered on a visa waiver that prohibited them from working.

Kang, the South Korean presidential chief of staff, said that South Korea will push to review and improve visa systems for those traveling to the U.S. on business trips for investment projects.