Taiwan Semiconductor Manufacturing Co. discovered this month that chips it made for a specific customer ended up with Huawei Technologies, a potential violation of U.S. sanctions intended to sever the flow of technology to a Chinese national champion.

TSMC halted shipments to the client around mid-October after it realized semiconductors fabricated for that entity had found their way into Huawei products, a person with direct knowledge of the matter said. The chipmaker has since notified the U.S. and Taiwanese governments and is investigating the matter more thoroughly, the person said, asking not to be identified discussing a sensitive situation.

It’s unclear whether the TSMC client was acting on Huawei’s behalf, or where it’s based. But the incident sheds new light on reports that surfaced in past days, including from The Information, that Washington reached out to TSMC recently about whether the company had produced chips for the blacklisted Chinese company.