Washington is investigating whether China’s largest state-controlled telecom carriers are providing American data to Beijing through their US cloud services, Reuters reported, citing three sources familiar with the matter.

The Commerce Department is running a probe into the activities of China Mobile Ltd., China Telecom Corp. and China Unicom, the news agency said. They’ve subpoenaed information from the trio and conducted risk-based analyses of the companies, though they’re less advanced in their investigation of Unicom, Reuters cited the people as saying.

US government agencies have warned about potential security risks linked to Chinese state-owned telcos for years. Washington in 2022 decided to eject Unicom from the US market, after previously barring China Mobile. The companies and their US-based lawyers did not respond to requests for comment from Reuters.