Reuters learned of underage workers at the Hyundai-owned supplier following the brief disappearance in February of a Guatemalan migrant child from her family's home in Alabama.

The girl, who turns 14 this month, and her two brothers, aged 12 and 15, all worked at the plant earlier this year and weren't going to school, according to people familiar with their employment. Their father, Pedro Tzi, confirmed these people's account in an interview with Reuters.

Police in the Tzi family's adopted hometown of Enterprise also told Reuters that the girl and her siblings had worked at SMART. The police, who helped locate the missing girl, at the time of their search identified her by name in a public alert.

Reuters is not using her name in this article because she is a minor.