“I am deeply concerned. I feel heavy responsibility for the arrests of our citizens,” Cho told an emergency government meeting.

The incident could exacerbate tensions between the Trump administration and Seoul, a key Asian ally and investor. They have been at odds over the details of a trade deal that includes $350 billion of South Korean investment in the United States.

A video released by U.S. Immigration and Customs Enforcement showed Asian workers shackled at the wrists, waist, and ankles getting on a bus after the raid, which involved a helicopter and armoured vehicles.

In the video, hundreds of workers were standing up in front of a building, with some wearing yellow vests with names such as “Hyundai” and “LG CNS.” Two of the workers hid in a pond before being arrested.

“We welcome all companies who want to invest in the U.S., and if they need to bring workers in for building or other projects, that’s fine — but they need to do it the legal way,” Special Agent in Charge of Homeland Security Investigations in Georgia and Alabama Steven N. Schrank, said in a statement on Saturday.

“This operation sends a clear message that those who exploit the system and undermine our workforce will be held accountable.”

Hyundai said it would investigate its suppliers and their subcontractors to ensure they meet regulations.

LG Energy Solution, which is working with Hyundai to build the factory, said it had asked employees to return from U.S. business trips while suspending travel to the United States except for customer meetings.