A US senator is asking the Pentagon for more information on Microsoft’s reported use of Chinese engineers in maintaining military cloud computing systems, according to a copy of the letter seen by Reuters.

Senator Tom Cotton, an Arkansas Republican who chairs the chamber’s intelligence committee and also serves on its armed services committee, sent the letter to Defence Secretary Pete Hegseth after a report this week in investigative journalism publication ProPublica.

The report detailed Microsoft’s use of Chinese engineers to work on US military computing systems under the supervision of US “digital escorts” hired through subcontractors who have security clearances but often lacked the technical skills to assess whether the work of the Chinese engineers posed a cybersecurity threat.

Contacted by Reuters about the ProPublica report and Cotton’s letter, Microsoft declined to comment.

The company, a major contractor to the US government, has had its systems breached by Chinese and Russian hackers. It told ProPublica that it disclosed its practices to the US government during an authorisation process.

On Friday, Microsoft spokesman Frank Shaw said on social media that the company had changed how it supports US government customers “in response to concerns raised earlier this week … to assure that no China-based engineering teams are providing technical assistance” for services used by the Pentagon.