Immigration officials arrested nearly 500 workers, most of them South Korean nationals, at the construction site of an electric vehicle battery plant in Georgia on Thursday, as the Trump administration continues its far-ranging crackdown on illegal immigration.

The raid, which U.S. officials have called the largest-ever Homeland Security enforcement operation at a single location, stirred tensions with the South Korean government, a valued trade partner of the United States. It also revealed competing interests within the Trump administration between the president’s push to expand manufacturing in the United States and his aggressive efforts to crack down on immigration. The plant at the center of the operation was co-owned by the South Korean carmaker Hyundai.

U.S. immigration authorities said the detained employees — many of them hired by subcontractors to help finish the plant’s construction — were working or living in the United States illegally.

On Sunday, government officials with South Korea said they had reached an agreement with the United States to free the Korean workers and fly them back to that country.

Here’s what we know about the raid and its fallout:

Where did it happen?

The raid targeted an electric vehicle battery plant still under construction in Ellabell, Ga., near Savannah. The plant is owned by two companies: Hyundai Motor Group and LG Energy Solution, both titans in South Korean industry.

Immigration officials descended on the plant on Thursday, arresting hundreds who were allegedly living or working in the United States illegally. The operation was the product of a monthslong investigation, officials said.