WASHINGTON (Reuters) -U.S. officials say solar-powered highway infrastructure including chargers, roadside weather stations, and traffic cameras should be scanned for the presence of rogue devices - such as hidden radios - secreted inside batteries and inverters.

The advisory, disseminated late last month by the U.S. Department of Transportation's Federal Highway Administration, comes amid escalating government action over the presence of Chinese technology in America's transportation infrastructure. 

The four-page security note, a copy of which was reviewed by Reuters, said that undocumented cellular radios had been discovered "in certain foreign-manufactured power inverters and BMS," referring to battery management systems. 

The note, which has not previously been reported, did not specify where the products containing undocumented equipment had been imported from, but many inverters are made in China.

There is increasing concern from U.S. officials that the devices, along with the electronic systems that manage rechargeable batteries, could be seeded with rogue communications components that would allow them to be remotely tampered with on Beijing's orders.

In May, Reuters reported that American energy officials had become concerned after experts found rogue communication devices in some Chinese inverters and batteries. Later that month, industry group Green Power Denmark said that unexplained electronic components had been found in imported equipment for Denmark's energy supply network.

The U.S. Cybersecurity and Infrastructure Security Agency referred questions to the Department of Transportation, which said in a statement that the advisory "summarizes public and unclassified reporting to ensure agencies are implementing practical mitigation steps for transportation operators." It referred further questions back to the Cybersecurity and Infrastructure Security Agency.

The Chinese Embassy in Washington said in a statement that it opposed "the distortion and smear of China's achievements in the field of energy infrastructure."

In its advisory, the Federal Highway Administration warning cited federal and state-level reporting about "undocumented cellular radios" found inside inverters and batteries and that national-level assessments had determined that they could pose a risk.

The August 20 advisory said the devices were used to power a range of U.S. highway infrastructure, including signs, traffic cameras, weather stations, solar-powered visitor areas and warehouses, and electric vehicle chargers. The risks it cited included simultaneous outages and surreptitious theft of data.

The alert suggested that relevant authorities inventory inverters across the U.S. highway system, scan devices with spectrum analysis technology to detect any unexpected communications, disable or remove any undocumented radios, and make sure their networks were properly segmented.

Separately, Washington has also raised concerns over the presence of Chinese autos on U.S. highways, worrying that Chinese companies could collect sensitive data while testing autonomous vehicles in the United States.

In January, the Commerce Department finalized rules that will effectively bar nearly all Chinese cars and trucks from the U.S. market by late 2026, as part of a crackdown on vehicle software and hardware from China.