Jakarta, CNBC Indonesia - Hundreds of workers at a Hyundai Motor car battery facility under construction in Georgia were detained in a raid by US authorities on Thursday, halting work at the plant, one of the Korean automaker's major investments in the US.

About 475 workers, most of whom were South Korean citizens, were arrested, according to US immigration officials, the largest single-site law enforcement operation in the history of the US Department of Homeland Security (DHS).

As reported by Reuters, President Donald Trump's administration has stepped up its crackdown on immigrants, disrupting businesses across the country, even as the White House has pushed for more inflows from foreign investors.

The arrests could exacerbate tensions between Washington and Seoul, major US allies and investors. The two countries have been at odds over details of a trade deal that includes $350 billion in investment. At a summit last month, South Korea pledged $150 billion in US investment—including $26 billion from Hyundai Motor.

Homeland Security officials said the workers arrested at the Ellabell, Georgia, location were barred from working in the US after crossing the border illegally or overstaying their visas.

"The investigation has been going on for several months," Steven Schrank, special agent in charge of the investigation for Georgia, said at a news conference.

"This isn't an immigration operation where agents enter the site, round up people, and put them on buses," he said. Schrank said there is a network of subcontractors at the site.

"The arrested workers are being held at the ICE detention facility in Folkston, Georgia. Most of the 475 are South Korean citizens," Schrank said.

A Hyundai Motor spokesman said none of those detained worked directly at the car company.

The company said that its head of manufacturing for North America, Chris Susock, will “take over governance of the entire megasite in Georgia.”

"We will conduct investigations to ensure all suppliers and their subcontractors comply with all laws and regulations. Hyundai will not tolerate anyone who does not comply with the law," the company said in a statement.

Korean media put the number of South Koreans detained at around 300. The raid—dubbed"Operation Low Voltage"—involved more than 400 law enforcement officers following a months-long investigation.

A spokesperson for Hyundai's battery joint venture partner, South Korean battery maker LG Energy Solutions, said in a statement that they are working together and have temporarily halted construction work. The facility, a joint venture between LGES and Hyundai Motor, is scheduled to begin operations later this year, according to LGES.

Hyundai Motor shares closed down 0.7% on Friday, and LGES shares fell 2.3%.

Under Trump's leadership, Immigration and Customs Enforcement, or ICE, part of DHS, has pushed the Republican leader's crackdown on migrants, backed by record-breaking funding and new powers to conduct raids.

Trump has said he wants to deport the"worst of the worst" criminals, but ICE data shows an increase in the number of non-criminals being apprehended. Human rights activists have condemned such raids.

The White House said Friday that"any foreign workers brought in for specific projects must enter the United States legally and with appropriate work authorization."

South Korea's Foreign Ministry expressed regret and concern over the raid.

"The economic activities of our companies investing in the United States and the interests of our citizens must not be unduly infringed upon during US law enforcement proceedings," ministry spokesman Lee Jae-woong said in a statement on Friday.

Videos on social media show a man wearing a vest marked HIS, an acronym for Homeland Security Investigations, instructing workers in yellow safety vests.

"We have a search warrant for the entire site. We want construction to stop immediately. We want all work on that site to stop immediately."

The US Justice Department said in a statement that several people attempted to escape during the raid. Some had to be sucked out of a waste pool at the site, the Justice Department said.

The Georgia Democratic Party condemned the raids, calling them part of a"politically motivated scare tactic designed to terrorize the people who work hard to earn a living, drive our economy, and contribute to the communities across Georgia they have called home."

In a statement, a spokesman for Georgia Governor Brian Kemp said:"In Georgia, we will always enforce the law, including all state and federal immigration laws."

Hyundai said its electric vehicle production at the sprawling site was unaffected.

In 2023, Hyundai Motor and LG Energy announced a $4.3 billion partnership to produce electric vehicle (EV) battery cells, with each company holding a 50% stake. The plant will supply batteries for Hyundai, Kia, and Genesis EV models.

The battery plant is part of Hyundai's $12.6 billion investment in the state, including the automaker's recently opened car plant, which will be its largest economic development project, opening a new chapter in the state's history.