Auto Safety Regulator Investigating Tesla Recall of Autopilot

The federal government’s main auto safety agency said on Friday that it was investigating Tesla’s recall of its Autopilot driver-assistance system because regulators were concerned that the company had not done enough to ensure that drivers remained attentive while using the technology.

The National Highway Traffic Safety Administration said in documents posted on its website that it was looking into Tesla’s recall in December of two million vehicles, which covered nearly all of the cars the company had manufactured in the United States since 2012. The safety agency said that it had concerns about crashes that took place after the recall and results from preliminary tests of recalled vehicles.

The investigation adds to a list of headaches for Tesla, the dominant electric vehicle maker in the United States. The company’s sales fell more than 8 percent in the first three months of the year compared with the same period a year earlier, the first such drop since the early days of the coronavirus pandemic.

Tesla announced in December that it would recall its autopilot software after an investigation by the auto safety agency found that the carmaker hadn’t put in place enough safeguards to make sure the system, which can accelerate, brake and control cars in other ways, was used safely by drivers who were supposed to be ready at any moment to retake control of their cars using Autopilot.

The agency said it had identified at least 13 fatal crashes tied to use of Autopilot. The company is also facing lawsuits from individuals who claim the system is defective, and its design contributed to or is responsible for serious injuries and deaths.

The recall, which entails a wireless software update, includes more prominent visual alerts and