"Among other things, we require each of our infrastructure vendors to submit their equipment and software to extensive testing by a leading third party recognized for vetting critical infrastructure systems for security purposes before incorporating it into our network," Clearwire said.

Cricket Communications, a national low-cost cellular carrier, also said it uses network gear from multiple vendors. A majority of its network is not built with Huawei equipment, Cricket said in a statement. The company said it has systems to monitor its network and identify intrusions. "We are respectful of the committee's findings and will consider them carefully and thoughtfully," Cricket said.

Global wired backbone provider Level 3 wouldn't comment on Huawei in particular but said it has an extensive security system to safeguard its network.

"Telecommunications gear and the components used in making that gear come from all over the world," Level 3 said in a statement. "We follow a stringent set of security protocols that includes extensive testing and monitoring of all vendor equipment."

It's common for service providers to go to multiple vendors for network equipment, to avoid dependence on one vendor.