They were flown in under visas to help set up the plant as consultants (at least at one of the plants). I don't think they were intended to continue working there after. Some of the visas were also expired.

The article also says:

> LG Energy Solution said Saturday that 47 of its employees were detained, 46 of them Korean. Another 250 personnel from “equipment partner companies,” most of them Korean, were also being held, it added.

So it seems there were multiple parent companies involved