KPN said that it is not aware of any improper access by Huawei employees, and Huawei, the biggest supplier of equipment for KPN's 4G mobile networks, denied the report.
The Agentschap Telecom said in a statement it would also check whether KPN's current security measures are adequate and issue first findings "in about a month".
"It's a once-in-a-generation investment in America, unlike anything we've seen or done since we built the interstate highway system and the space race decades ago."