The U.K. government warned on Thursday Huawei’s telecommunications equipment raises “significant” security issues, posing a possible setback to the Chinese tech firm as it looks to build out 5G networks.

46-page report evaluating Huawei’s security risks, British officials stopped short of calling for a ban of Huawei’s 5G telecommunications equipment. But the assessment cited “underlying defects” in the company’s software engineering and cybersecurity processes, citing “significantly increased risk to U.K. operators.”

The findings give weight to warnings from U.S. officials who have argued Huawei’s networking equipment could be used for espionage by the Chinese government. Huawei has repeatedly said it does not pose any risk and insists it would not share customer data with Beijing.

In a statement Thursday, Huawei said it takes the U.K. government’s findings “very seriously.”

“The issues identified in the OB (oversight board) report provide vital input for the ongoing transformation of our software engineering capabilities,” a Huawei spokesperson said.

This is a developing story. Check back later for updates.