Musk's Tesla has been investigated by the US over the safety of its self-driving software

The US agency responsible for regulating road safety revealed on Friday that it is investigating Tesla's self-driving software systems.

The National Highway Traffic Safety Administration's (NHTSA) assessment covers 2.4 million Tesla vehicles across multiple models made between 2016 and 2024.

NHTSA's move is the first step toward any potential recall the agency could seek against the company, which is run by tech billionaire Elon Musk.

Tesla did not immediately respond to a BBC inquiry on Friday about the investigation.

NHTSA's initial assessment follows four crash reports involving the use of Tesla's “full self-driving,” or FSD, software.

The agency said the crash was associated with reduced road visibility due to fog or sunlight.

NHTSA said one Tesla fatally struck a pedestrian and another injured one.

The evaluation aims to determine whether Tesla's self-driving systems can detect and respond appropriately to reduced visibility conditions. It will also examine whether other self-driving accidents have occurred under similar conditions.

In its announcement, the company noted that despite the label, fully self-driving is actually “a partial driving automation system.”

NHTSA's announcement comes a week later Mr. Musk's glitzy rollout of CyberCab on the Warner Bros. studio lot in Burbank, California.

At the event, Mr Musk said fully autonomous robotaxis concepts, which operate without pedals or steering wheels, could be on the market by 2027.

But some analysts and investors were unprepared.

The company's stock has fallen 8% since CyberCab's launch. Shares were mostly steady after the notice from NHTSA.

Unlike Waymo, the self-driving venture run by Google-parent Alphabet, Tesla's autonomous systems rely largely on cameras and artificial intelligence.

Mr. Musk's approach costs less than deploying high-tech sensors like lidar and radar, which are critical to Waymo's driverless car program.