Apple is looking into its Apple Watch supply chain after a report was published last week claiming its manufacturer relied on student interns to complete the devices, according to the Financial Times. Sacom, a human rights group, claims Quanta Computer, a Taiwanese Apple supplier, employed students illegally and required them to work overtime and night shifts with only one day off per week. Sacom says Quanta exclusively manufactures the Apple Watch Series 1, 2, and 4 and is the main manufacturer of the Series 3.

The group says it interviewed 28 high school students at the Quanta Computer factory in Chongqing, China, this summer. Most of them were aged between 16 and 18 and performed rote tasks on the production line.

The students claim their teachers told them they wouldn’t be able to graduate on time without this work. One student majoring in auto repair told the group: “I told my teacher I do not want to do this job. He then called my father and talked to him for more than an hour. My father then pressured me, so I had no choice but to come.”

Sacom claims that many of the students’ majors had nothing to do with electronics and that they saw no benefit from this internship that involved assembling parts for 12 hours a day, sometimes from 8PM to 8AM. We’ve reached out to Apple for comment on the story, but in the meantime, the company issued a statement to the Financial Times and said:

“We are urgently investigating the report that student interns added in September are working overtime and night shifts. We have zero tolerance for failure to comply with our standards and we ensure swift action and appropriate remediation if we discover [supplier code] violations.”

We’ll update if we hear more from Apple.