South Korea reached a deal with the US to free hundreds of South Korean workers arrested when the US immigration authorities raided the construction site of a battery plant in Georgia, the country’s presidential office said on Sunday.

“There are some administrative procedures left, but once they are cleared, we will send a chartered plane to bring our people home,” Kang Hoon-sik, the chief of staff for President Lee Jae Myung of South Korea, told a meeting of senior officials from the administration and the governing Democratic Party on Sunday.

Kang provided no further details, including when South Korea expected to send the plane. But his remarks provided the first strong indication that South Korea and the US were working out a diplomatic solution after days of tensions between the allies.

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

US immigration officials stormed the construction site of a major Hyundai-LG electric vehicle battery plant in Ellabell, Georgia, on Thursday, arresting 475 people. Of them, about 300 were South Korean citizens, the South Korean foreign minister’s office said.

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 unsettled South Korea, a crucial US ally that has been asked to invest billions of dollars in the US to build new factories and create jobs. It was part of the Trump administration’s aggressive crackdown on immigration, and US officials said those arrested were in the US illegally or working unlawfully.

“We will not let our guard down until we have our people safely back home,” Kang said. “We will also review and improve the visa system for those who go to the US on business trips related to investment projects so that similar incidents won’t be repeated.”

The raid brought construction to a halt at the Georgia factory. Kang confirmed on Sunday that South Korea was still committed to finishing the project.

President Lee said the rights of South Korean nationals and the economic activities of South Korean companies must not be unfairly infringed upon during the US 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.

The Trump administration has encouraged South Korean industrial giants such as Hyundai, Samsung and LG to invest in the US. But the administration has also drastically tightened visa allocations, making it more difficult for them to bring cheap and skilled workers to build their factories.

Those arrested included dozens of LG workers who were on business trips with various visas or under a visa waiver programme to provide technical guidance for building the battery factory, according to industry officials familiar with the project. Other detained South Korean workers had been hired by construction subcontractors working for Hyundai and LG, they said.

US immigration officials accused the South Korean companies of discriminating against American workers by hiring unauthorised workers from abroad.

New York Times News Service and AP