WASHINGTON, United States (AFP)-South Koreans suspected of working in the United States illegally were the majority of the 475 people arrested in a raid on a Hyundai-LG battery plant being built in the southern state of Georgia, a US official said Friday.

The raid came as President Donald Trump cracks down on migrants across the country, vowing to carry out the largest deportation drive in US history.

Thursday’s operation stemmed from a “criminal investigation into allegations of unlawful employment practices and serious federal crimes,” Steven Schrank, a Homeland Security Investigations special agent in Atlanta, said.

“This, in fact, was the largest single site enforcement operation in the history of Homeland Security Investigations,” Schrank said at a press conference.

South Korea has expressed “concern and regret” over the raid to the US Embassy in Seoul and urged Washington to respect the rights of its citizens.

“The economic activities of our investors and the legitimate rights and interests of our nationals must not be unjustly infringed in the course of US law enforcement,” South Korean foreign ministry spokesperson Lee Jae-woong told reporters.

Schrank said the 475 arrested at the Hyundai Motor-LG Energy Solution joint venture plant in the town of Ellabell were “illegally present in the United States” and “working unlawfully.”

“There was a majority of Korean nationals from the 475,” he said.

In Seoul, a source familiar with the matter told AFP that around 300 South Korean nationals had been detained.

Schrank said he could not give a breakdown of how many of those arrested at the plant, which is intended to supply batteries for electric vehicles, were employed by Hyundai, LG or subcontractors.

Those taken into custody have been turned over to US Immigration and Customs Enforcement (ICE) for potential removal, he said.

“We are sending a clear and unequivocal message that those who exploit our workforce, undermine our economy and violate federal laws will be held accountable,” he said.