Federal agents targeting illegal employment practices have detained nearly 500 workers, the majority of them South Koreans, at a Hyundai battery plant in Georgia.

The Sept. 4 raid at the under-construction HL-GA Battery Company plant in Ellabell, about 30 miles northwest of Savannah, was not primarily an immigration action but instead focused on criminal violations of employment laws, officials said at a Sept. 5 news conference.

"The goal of this operation is to reduce illegal employment and prevent employers from gaining an unfair advantage by hiring unauthorized workers," U.S. Attorney Margaret E. Heap said.

About 475 people were detained in the raid at the $4.3 billion construction site. Federal officials said the raid was the largest single-site workplace enforcement action in the history of Homeland Security Investigations.

The factory will make batteries for Hyundai cars built in the United States.