Apple has reprimanded one of its largest manufacturers after a Financial Times investigation found that thousands of student interns had worked overtime to assemble iPhones, in breach of Chinese law.

After being contacted by the FT, Apple said it had stopped giving “new business” to Pegatron, its second-largest iPhone assembler after Foxconn. However, workers there said the factory was still manufacturing new products ahead of the holidays.

Apple is racing to make up for production delays earlier in the year caused by the pandemic. The latest revelations of supply chain abuses will come as an embarrassment to the company during its busiest season for new product launches in years. The latest iPhone 12 models are set to go on sale on Friday, two months later than normal. At an event on Tuesday, Apple is also expected to reveal new Mac computers.