The National Highway Traffic Safety Administration has expanded its investigation into Tesla's Full Self-Driving system, focusing on the technology's performance during poor road visibility conditions, according to reports.

The federal safety probe centers on Tesla vehicles equipped with Full Self-Driving capabilities and their ability to operate safely when cameras cannot clearly see road conditions. Tesla's system includes what the company calls a "degradation detection" feature designed to alert drivers to take manual control when the vehicle's cameras encounter visibility issues.

The investigation represents an escalation of regulatory scrutiny over Tesla's autonomous driving technology. NHTSA has been examining various aspects of Tesla's driver assistance systems as part of its broader oversight of emerging automotive technologies.

Tesla's Full Self-Driving system relies primarily on cameras and computer vision to navigate roads, rather than additional sensors like radar or lidar used by some competitors. This camera-based approach has drawn attention from safety regulators, particularly regarding performance in challenging weather or lighting conditions.

The outcome of the expanded investigation could potentially lead to regulatory action affecting Tesla vehicles currently on the road. NHTSA has authority to order recalls or other safety measures if it determines a vehicle system poses unreasonable safety risks to drivers or other road users.