The immigration raid last week on an electric vehicle battery plant in Georgia owned by two South Korean manufacturers was yet another setback for what had been a fast-growing industry in the United States.

The sector was already beleaguered by lower-than-expected demand for electric vehicles, tariffs on raw materials and the rapid phaseout of a federal tax credit for purchases of E.V.s, which have led companies to delay or scale back production.

But the raid at the plant under construction in Ellabell, Ga., which is owned by the carmaker Hyundai and battery supplier LG Energy Solution, raised more risks for foreign manufacturers in the United States. Immigration officials arrested 475 people. Of them, about 300 were South Korean citizens, according to the South Korean foreign minister’s office.

It is not yet clear how many of those detained by ICE last week were building the plant and how many were workers brought in to install and calibrate specialized equipment, or to train the local work force.

Some American workers in the area have complained that they have not been given a fair chance at employment at the $7.6 billion taxpayer-subsidized complex, which has been billed as the largest economic development project in Georgia’s history.

These labor tensions have been building as the federal government, seeking a stronger foothold in the battery business, has wooed foreign companies to expand manufacturing on U.S. soil.