Many of the car workers arrested in a huge US workplace immigration raid had violated their visitor visas, officials say.

Immigration and Customs Enforcement (ICE) said 475 people, mostly South Korean citizens – were found to be illegally working at a Hyundai battery plant in the state of Georgia on Thursday.

“People on short-term or recreational visas are not authorized to work in the US,” ICE said, adding that the raid was necessary to protect American jobs.

South Korea, whose companies have promised to invest billions of dollars in key US industries in the coming years, partly to avoid tariffs, has sent diplomats to Georgia, and called for its citizens’ rights to be respected.

The arrested workers were being held at an ICE facility in Folkston, Georgia, until the agency decides where to move them next.

Of those detained, 300 are reported to be Korean nationals. Hyundai said in a statement that none of them were directly employed by the company.

LG Energy Solution, which operates the plant with Hyundai, told the BBC its top priority was to ensure the safety and wellbeing of its employees and partners and that it “will fully cooperate with the relevant authorities”.

In a statement on Friday, the ICE office in the city of Savannah said the raid was “part of an active, ongoing criminal investigation”.

“The individuals arrested during the operation were found to be working illegally, in violation of the terms of their visas and/or statuses,” the statement added.

But Charles Kuck, an immigration lawyer in Atlanta, told the New York Times that two of his clients were wrongly caught up in the raid.

He told the newspaper the pair were in the US under a visa waiver programme that allows them to travel for tourism or business for up to 90 days.

“My clients were doing exactly what they were allowed to do under the visa waiver – attend business meetings,” he said on Friday.

He said one of them only arrived on Tuesday and was due to leave next week.

ICE said one of those detained was a Mexican citizen and green card holder with a lengthy rap sheet.

The individual had previously been convicted of possession of narcotics, attempting to sell a stolen firearm and theft, according to ICE.

Homeland Security Investigations (HSI) Special Agent Steven Schrank said: “We welcome all companies who want to invest in the US.

“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.

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

South Korea’s foreign ministry responded to the raid with a statement saying: “The economic activities of Korean investment companies and the rights and interests of Korean citizens must not be unfairly infringed upon during US law enforcement operations.”

The raid raises a possible tension between two of President Donald Trump’s top priorities – building up manufacturing within the US and cracking down on illegal immigration. It could also put stress on the country’s relationship with a key ally.

President Trump said in the Oval Office on Friday: “They were illegal aliens and ICE was just doing its job.”

Asked by a reporter about the reaction from Seoul, he said: “Well, we want to get along with other countries, and we want to have a great, stable workforce.

“And we have, as I understand it, a lot of illegal aliens, some not the best of people, but we had a lot of illegal aliens working there.”

Trump has worked to bring in major investments from other countries while also levying tariffs he says will give manufacturers incentives to make goods in the US.

The president also campaigned on cracking down on illegal immigration, telling supporters he believed migrants were stealing jobs from Americans.

The factory, which makes new electric vehicles, had been touted by Georgia’s Republican governor as the biggest economic development project in the state’s history, employing 1,200 people.