The National Highway Traffic Safety Administration on Thursday escalated its probe into 3.2 million Tesla vehicles with Full Self-Driving driver-assistance on concerns the system may fail to detect or warn drivers in poor visibility.

NHTSA first opened a preliminary evaluation into the automaker’s FSD software in October 2024 in 2.4 million vehicles. The agency is now opening an engineering analysis, a required step before it can seek a recall.

The agency said its investigation raises concerns the Tesla camera-based system did not detect common roadway conditions like glare, dust or other airborne obstructions that impaired camera visibility, or provide alerts when camera performance deteriorated until immediately before a crash.

NHTSA said it had reports of nine incidents that may be tied to the issue including one fatal crash and two injury crashes, and was investigating whether six other crashes may be related.

FSD is an assistance system that Tesla says takes care of the most stressful parts of daily driving but requires drivers to pay attention and intervene if needed.

The investigation, which covers most Tesla vehicles on U.S. roads, adds to the regulatory scrutiny of the self-driving technology central to Tesla’s ambition to build a fleet of robotaxis that would underpin its future, as the company shifts focus away from an ailing auto business.

NHTSA said when Tesla began transitioning away from

using both cameras and radars to an exclusively camera-based approach, known as Tesla Vision in mid-2021, it implemented a degradation detection system. NHTSA said the data raises concerns the system fails to detect or warn drivers appropriately under degraded visibility conditions.

In many of the crashes reviewed, “FSD also lost track of or never detected a lead vehicle in its path,” it said.

The agency has opened numerous investigations into the performance of Tesla’s advanced driver assistance systems like Autopilot and FSD.

In October, it launched a separate investigation into 2.88 million Tesla vehicles equipped with FSD over more than 50 reports of traffic safety violations and a series of crashes.

The auto safety agency said FSD has “induced vehicle behavior that violated traffic safety laws.”

Tesla did not immediately respond to a Reuters request for comment.

The company’s analysis showed that if an update to the degradation detection system was installed at the time of the crash, it may have affected three of the incidents, NHTSA said.

The agency plans to examine the performance of the updated system, including when it was deployed, how widely it has been rolled out and whether it improves the system’s ability to detect visibility issues and alert drivers in time.

Two of the crashes NHTSA identified also involved injuries.

(Reporting by Akash Sriram in Bengaluru and David Shepardson in Washington; Editing by Shinjini Ganguli, Anil D’Silva and Pooja Desai)