U.K. cybersecurity.officials are concerned that Huawei has still not patched issues with its.routers leaving networks open to compromise.

 Ian Levy, technical director of Britain’s National Cyber Security Center, told The Washington Post that there are “worrying engineering issues” that have not been addressed by the company. Huawei was raised as the U.K. is in the process of contemplating the roll out of 5G and whether or not to join the United States in banning equipment from the Chinese company.

The U.S. has not only banned the use of Huawei products, but has filed criminal charges against Chinese telecommunications firm Huawei alleging the company stole intellectual property from T-Mobile and violated U.S. sanction orders and has started extradition proceedings against Huawei CFO Meng Wanzhou, who was arrested in Vancouver, Canada, late last year. Wanzhou is the daughter of Huawei’s founder.