The National Highway Traffic Safety Administration disclosed Friday that it’s opened a query into the Autopilot recall Tesla conducted in December. The agency is concerned as to whether the company’s remedy was sufficient, in part due to 20 crashes that have occurred involving vehicles that received Tesla’s over-the-air software update.

More than 2 million Tesla vehicles are subject to the probe, according to NHTSA. The carmaker’s shares fell as much as 1.7% shortly after the start of regular trading and are down more than 30% this year.

The investigation cuts against Chief Executive Officer Elon Musk’s exuberance about Tesla’s automated-driving systems. The billionaire has set a date in August to unveil a driverless robotaxi, which he said five years ago would be ready by 2020. During an earnings call this week, he downplayed the difficulty of getting the green light from regulators for that vehicle.

“I actually do not think that there will be significant regulatory barriers, provided there is conclusive data that the autonomous car is safer than a human-driven car,” Musk said. Later in the call, he said that those who doubt Tesla’s ability to “solve” autonomy shouldn’t invest in the company.

Tesla filed its Autopilot recall in December to address concerns NHTSA raised as part of a years-long defect investigation. A portion of the company’s remedy both requires car owners to opt in and allows drivers to readily reverse changes Tesla has made, according to the agency.

The carmaker also has deployed Autopilot updates separate from the one disclosed in its December recall that appear to be related to concerns NHTSA had raised as part of its defect probe, the agency said. The latest query will consider why these updates weren’t a part of the recall, NHTSA said.

Tesla has taken heat before from NHTSA over deploying software updates to Autopilot without filing a recall. The company did so in September 2021 weeks after the agency opened its defect investigation into the driving system.