WASHINGTON U.S. Transportation Secretary Pete Buttigieg said on Thursday his agency has national security concerns about Chinese autonomous vehicle companies in the American market after some lawmakers called for restrictions on their operations.

"Whether we are talking about hardware or software, in the same way there are concerns around telecom or TikTok, there are concerns around transportation technologies," Buttigieg said in an interview with Reuters.

Buttigieg said the United States needs to better understand "the true ownership of the different enterprises that are supplying different elements of our transportation systems."

In a July 17 letter to Buttigieg and Secretary of Commerce Gina Raimondo, a bipartisan group of four lawmakers asked for an investigation into the prevalence of Chinese AV technology in the United States and how it can be restricted.

"Technology used by AVs, LiDAR, RADAR, cameras, AI and other advanced sensors and semiconductors can all be used to collect data on the American people and infrastructure that could be shared back to China and ultimately to the Chinese Communist Party (CCP)," the lawmakers wrote.

The lawmakers were particularly concerned about AV vehicle and equipment testing in the United States.

Their letter cites data from California regulators showing seven Chinese firms, including Baidu's Apollo and robotaxi startup Pony.ai, tested autonomous vehicles in the most-populous U.S. state last year.

The autonomous vehicle industry in the U.S. has been late delivering on promises of commercializing cars that drive themselves.

Many AV companies have cut costs and jobs with some such as Ford and Volkswagen -backed Argo AI shutting shop. Major players still pursuing development include General Motors' Cruise unit, Alphabet's Waymo and Amazon's Zoox.

(Reporting by Chris Sanders and Abhirup Roy; Editing by Will Dunham and Cynthia Osterman)