Some of the claims in the original Fox News article are true. The article says that there is a surge of unaccompanied children at the border who are being exploited and have to resort to "indentured servitude to pay back smugglers and have worked in dire conditions."
CBS News agrees with the statement that migrants are being subjected to child labor: "After being released from federal custody, migrant children, most of whom are teenagers, often end up working grueling and dangerous jobs in factories, meat plants and construction sites that violate federal child labor laws."
This NBC article also agrees that migrant children are being exploited, citing an investigation by the Department of Homeland Security that is looking into "whether a human smuggling scheme brought migrant children to work in multiple slaughterhouses for multiple companies across multiple states."