Apple Inc. has put a supplier on probation after violence broke out at the supplier’s facility near Bengaluru, India, over alleged nonpayment to contingent workers, Reuters reported. Apple will not award Wistron Corp. new business at its iPhone factory until it has addressed the way workers were treated. Apple noted the company breached its “Supplier Code of Conduct.”

Violence broke out Dec. 13 at the facility and iPhone production was temporarily stopped. One official said six staffing firms that provide temporary workers to the facility could be blacklisted for failing to pay wages and that there were 8,500 temporary workers at the site.

However, staffing firms said last week they are looking into the situation and have a zero-tolerance policy for noncompliance.

CNN reported that Apple had placed another supplier, Pegatron, on probation last month for violating its labor code by having some student workers in China work nights and overtime. However, CNN reported a protest against Pegatron last week that included up to 500 temporary workers.

Apple regularly monitors suppliers and releases an annual report on steps it’s taking to ensure compliance with Apple’s rules. The most recent report came out last May.