Hundreds of people including South Korean workers were arrested in an immigration raid at a Hyundai Motor battery plant under construction in Georgia, weeks after the carmaker pledged $26 billion in U.S. investments.

South Korea protested the action to the U.S. and said it was trying to secure the release of its citizens.

The raid and arrests come after months of tense negotiations between the U.S. and South Korea over tariffs and investment. In late July, the two countries agreed that a 15% tariff rate would be imposed on South Korean imports in exchange for South Korea investing $350 billion in the U.S.

The factory is being built by a joint venture between South Korea-based Hyundai Motor and a South Korean battery manufacturer, LG Energy Solution. It is located in the town of Ellabell, near Savannah, Ga., and is part of a $7.6 billion Hyundai complex that the state has described as the largest manufacturing project in Georgia’s history.

President Donald Trump announced on Sunday that the U.S. will allow foreign companies to temporarily bring in “people of expertise” to train American workers, after which these experts would return to their home countries. “If we didn’t do this,” the president wrote on social media, “massive investment will never come.”

He may be too late. An Immigration and Customs Enforcement raid on a Hyundai-LG plant earlier this month, in which 475 workers, many of them South Korean, were detained in shackles, has already prompted South Korean businesses to suspend at least 22 projects in the U.S. cumulatively worth more than $100 billion.