TAIPEI (Taiwan News) — Taiwan Semiconductor Manufacturing Company (TSMC) has stopped shipments to at least two chip developers over their possible ties to Chinese electronics company Huawei, sources familiar with the matter said.

The two companies had placed orders for chips produced using TSMC’s 7nm (nanometer) process, Nikkei Asia reported on Tuesday (Oct. 29). The increasing order volumes raised TSMC’s suspicions, sources said, per CNA.

“We maintain a robust and comprehensive export system for monitoring and ensuring compliance,” TSMC said. “If we have any reason to believe there are potential issues, we will take prompt action to ensure compliance, including conducting investigations and proactively communicating with relevant parties.”

Meanwhile, TSMC suspended shipments to Chinese company Sophgo after a chip it made was found on Huawei’s Ascend 910B chiplet, sources said, per Reuters. However, Sophgo said it never engaged in a business relationship with Huawei.

The US has been strengthening its export control measures in key semiconductor supply chain hubs such as Taiwan, Japan, and South Korea. It restricts chip making equipment containing US technology from being used to make 14nm chips or better for Chinese companies without an export license.