The Hyundai factory workers were here in legal visas

According to ICE and US officials, the majority of the approximately 475 detained workers were South Korean nationals who had entered the US on visitor visas (B-1/B-2), which do not permit employment. These workers were found to be working illegally, violating the terms of their visas.bbc.combbc.comICE raid on Hyundai plant in Georgia swept up workers on visitor visasnytimes.comnytimes.comSouth Koreans Are Swept Up in Immigration Raid at Hyundai Plant in Georgia

The BBC explicitly states that many of the workers had violated their visitor visas by working at the plant. This is consistent with reports from ABC News and other outlets describing the raid as targeting unauthorized employment rather than visa overstays or undocumented entry.abc.net.auabc.net.auWhat to know about the Hyundai immigration raid in US+1 more

A Reddit discussion notes that these workers did not come as immigrants intending to settle but entered legally on visitor visas brought by Hyundai to assist with setting up operations. However, this does not equate to having legal work authorization; visitor visas do not allow employment.reddit.comreddit.comr/OutOfTheLoop on Reddit: What's the deal with 300 migrants working at a Hyundai...

The South Korean government’s involvement in repatriating over 300 detained workers further underscores their irregular status in terms of US work authorization.washingtonpost.comwashingtonpost.comSouth Korea announces deal to repatriate workers detained in Hyundai raidapnews.comapnews.comSouth Korea will bring home 300 workers detained in massive Hyundai plant raid...+1 more

No credible source indicates that these workers held proper work visas such as H-1B, L-1, or other employment-based visas. Instead, the consensus is that they were working in violation of their visitor visa status.