WASHINGTON (Reuters) -The Federal Communications Commission said on Friday it is investigating nine Chinese companies including Huawei Technologies, ZTE (Shenzhen:000063), Hangzhou Hikvision, China Mobile, China Telecom and others to determine if they are seeking to evade U.S. restrictions.

The Chinese companies have all been placed on the FCC's "Covered List" that deems specific communications equipment and services pose a threat to U.S. national security.

FCC Chair Brendan Carr said the companies may be still operating in the United States because they do not believe the designation prohibits particular types of operations. Other companies under investigation include Hytera Communications, Dahua Technology Company, Pacifica Networks/ComNet and China Unicom (Americas).

It is the latest in a series of actions against Chinese telecom and technology firms by Washington. The FCC previously barred the Chinese companies from providing telecommunications services in the United States, citing national security concerns.

The companies did not comment or immediately respond to requests for comment.

Carr said the FCC has reason to believe some or all of the Chinese firms on the list "are trying to make an end run around those FCC prohibitions by continuing to do business in America on a private or 'unregulated' basis."

He said the FCC "will identify the scope of their ongoing activities and move quickly to close any loopholes that have permitted untrustworthy, foreign adversary state-backed actors to skirt our rules."

The FCC's investigation is seeking detailed information about ongoing U.S. businesses and information about other companies that may be aiding U.S. operations. The FCC sent Letters of Inquiry and at least one subpoena to the companies, the agency said.

The FCC last year advanced efforts to step up security of the Border Gateway Protocol, or BGP, which is central to the internet's global information routing system. The move came after U.S. agencies said China Telecom abused BGP vulnerabilities "to misroute United States internet traffic on at least six occasions."

(Reporting by David Shepardson; Editing by Kirsten Donovan)