SEOUL, South Korea (AP) -- South Korea's foreign minister departed for the U.S. on Monday to finalize steps for the return of several hundred South Korean workers detained in a massive immigration raid in Georgia, a spectacle that has caused confusion, shock and a sense of betrayal among many in the U.S.-allied nation.

The Sept. 4 raid on a battery factory under construction at a sprawling Hyundai auto plant resulted in the detainment of 475 workers, more than 300 them South Koreans. Some were shown being shackled with chains around their hands, ankles and waists in video released by U.S. Immigration and Customs Enforcement.

South Korea announced Sunday that the U.S. has agreed to release them and that it would bring them home on a charter flight once final administrative steps are completed.

President Donald Trump said the workers "were here illegally," and that instead, the U.S. needs to work out arrangements with countries like South Korea to bring their experts in to train U.S. citizens to do work such as battery and computer manufacturing.