A 2023 Tesla Model X sits outside a Tesla dealership in June 2023, in Englewood, Colo.  David Zalubowski/Associated Press, file

The National Highway Traffic Safety Administration has launched a new review of Tesla’s Autopilot system, signaling apprehension that the automaker did not do enough to remedy the regulator’s concerns for driver safety with its recall of 2 million cars equipped with the system in December.

In a memo dated Thursday, the agency said it was opening what’s known as a “recall query” and that it has “identified concerns due to post-remedy crash events and results from preliminary NHTSA tests of remedied vehicles.”

Tesla agreed to the recall following a string of deadly crashes and a two-year investigation by the NHTSA into whether Autopilot had enough safeguards to keep drivers alert while the system was engaged. In its December recall notice to consumers, the agency said it found that Autopilot’s key Autosteer feature “may not” have sufficient controls to “prevent driver misuse,” such as using the feature outside the controlled-access highways for which it was designed.

Tesla disputed the agency’s criticisms but said it solved the issue with software updates that added alerts to remind drivers to pay attention while using the automated driving system. The company did not limit where the system could operate, which experts at the time said would have been a better fix.

At least one fatal accident has involved a Tesla using Autopilot on a road with cross traffic, for which the car’s manual says it is not designed.

The NHTSA’s new action comes after testing the cars at its facility in Ohio. The agency memo said that parts of the fix issued by Tesla required drivers to opt in and could be easily reversed. The NHTSA also said it had questions about other more recent changes Tesla has made to Autopilot that appeared to be linked to regulators’ concerns.

The review showcases the intense scrutiny Tesla is under from federal regulators, who reviewed more than 900 crashes involving Autopilot as part of the investigation.

It also underscores the NHTSA’s limited authority. The agency can investigate safety problems and order recalls, but it cannot tell vehicle manufacturers how to fix the issues that investigators uncover.

The NHTSA said it kept the investigation into Autopilot open even after the recall.

Tesla did not immediately respond to a request for comment on the new review early Friday.

The agency’s new action comes on the heels of a grim earnings report this week; Tesla reported a steeper-than-expected 55% plunge in profit amid lagging sales and increased competition. CEO Elon Musk has staked the company’s future on autonomous driving, recently promising to unveil a fully self-driving robotaxi in August.

At the same time, the company faces a string of lawsuits that allege Tesla exaggerated the true capabilities of its Autopilot technology and created a false sense of security for drivers who died or were seriously injured in crashes.

In court documents, the company maintains it is not liable for the crashes because it repeatedly warns drivers to remain in control of the vehicle.

December’s recall followed a Washington Post investigation that identified at least eight fatal or serious crashes on roads where Autopilot was not designed to be used.

The National Transportation Safety Board and others have asked federal regulators to force the company to limit use of the technology only to where it is designed to operate. The NHTSA has rejected that approach as too complex and resource-intensive.