U.S. auto safety regulators have opened an investigation into Tesla’s Model Y SUV after getting two complaints that the steering wheels can come off while being driven.

The National Highway Traffic Safety Administration says the probe covers an estimated 120,000 vehicles from the 2023 model year.

The agency says in both cases the Model Ys were delivered to customers with a missing bolt that holds the wheel to the steering column. A friction fit held the steering wheels on, but they separated when force was exerted while the SUVs were being driven.

The agency says in documents posted on its website Wednesday that both incidents happened while the SUVs had low mileage on them.

Messages were left seeking comment from Tesla, which has disbanded its media relations department.

In one complaint filed with NHTSA, an owner said he was driving with his family on Route 1 in Woodbridge, New Jersey, when the steering wheel suddenly came off on Jan. 29, five days after the vehicle was purchased. The owner wrote that there were no cars behind him, and he was able to pull toward the road divider. There were no injuries.

The complaint has a link to a Twitter posting from the owner that included a video of the detached steering wheel and pictures of the white Tesla being towed.

At first a Tesla service center gave the owner a cost estimate of $103.96 to repair the problem. The service center apologized in what appear to be text messages posted on Twitter.

When the owner wrote that he had lost faith in Tesla and asked for a refund, the service center removed the charge and wrote that Tesla doesn’t have a return policy, but he could reach out to the sales and delivery team.

The man was later given the option of keeping the car or getting it replaced with a new one, according to his post on Twitter. He posted that Tesla did replace his car.

Long String of Problems for Automaker

The investigation adds to a long string of problems that Tesla is having with the U.S. road safety agency. In the past three years it has opened investigations of Tesla’s “Autopilot” driver-assist system crashing into parked emergency vehicles, and problems with suspensions. At least 14 Teslas have crashed into emergency vehicles while using the Autopilot system.

The agency also is investigating complaints that Teslas can brake suddenly for no reason.

In February, NHTSA pressured Tesla into recalling nearly 363,000 vehicles with “Full Self-Driving” software because the system can break traffic laws. The system, which cannot drive itself, is being tested on public roads by as many as 400,000 Tesla owners. But NHTSA said in documents that it can make unsafe actions such as traveling straight through an intersection while in a turn-only lane, going through a yellow traffic light without proper caution or failing to respond to changes in posted speed limits.

The U.S. Justice Department also has asked Tesla for documents from Tesla about “Full Self-Driving” and Autopilot.

NHTSA has sent investigators to 35 Tesla crashes in which automated systems are suspected of being used. Nineteen people have died in those crashes, including two motorcyclists.

Since January of 2022, Tesla has issued 20 recalls, including several that were required by NHTSA. The recalls include one from January of last year for “Full Self-Driving” vehicles being programmed to run stop signs at slow speeds.