Amazon says that it’s investigating reports that its hardware supplier Foxconn, which produces Amazon Echo and Kindle hardware for the company, has violated labor laws by requiring teenaged workers to work overtime and night shifts, as reported by The Guardian.

The issue is specifically that the students — who are between the ages of 16 and 18 and are legally hired as “interns” — were working overtime and night shifts. Chinese labor laws allow students over the age of 16 to work in factories, but they prohibit overtime and night shifts. An account from China Labor Watch details the conditions at the factory further. In addition to the extra shifts (which the students are said to be forced to work by teachers or else they’ll be fired), the report also notes that student intern workers receive lower wages and poorer benefits.

Foxconn acknowledged to The Guardian that there was an issue, saying, “there have been instances in the past where lax oversight on the part of the local management team has allowed this to happen and, while the impacted interns were paid the additional wages associated with these shifts, this is not acceptable and we have taken immediate steps to ensure it will not be repeated.”

The company also said that it’s correcting the problem. “We have doubled the oversight and monitoring of the internship program with each relevant partner school to ensure that, under no circumstances, will interns [be] allowed to work overtime or nights.”

For its part, Amazon is also looking into the issue, with a spokesperson commenting, “We are urgently investigating these allegations and addressing this with Foxconn at the most senior level. Additional teams of specialists arrived on-site yesterday to investigate, and we’ve initiated weekly audits of this issue.”

This isn’t the first time Foxconn has had issues with underage Chinese workers working overtime, either. In 2017, Reuters reported that student workers were working extra shifts on assembling iPhone X phones. While those students were said to be pulling the extra hours voluntarily, Apple would go on to send staff to monitor the situation and ensure that the practice stopped.