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 Y vehicles were delivered to customers with a bolt that holds the wheel to the steering column missing. A friction fit held the steering wheels on, but they separated when force was exerted while the SUVs were being driven.

In one complaint filed with NHTSA, an owner said he was driving with his family 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.

“It was horrible experience. I was driving back from mall with family and in middle of freeway steering wheel fell off,” said Prerak Patel. “I was on the left lane when this happened. I can’t move my car to the left or right. However, I was lucky that road was straight and able to stop my car at the divider.”

The latest NHTSA investigation adds to a long string of problems that Tesla has had 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.

On Wednesday, the same day the report was aired on problematic Tesla steering wheels, U.S. safety regulators said a Tesla that crashed into a firetruck in California last month, killing the driver and injuring a passenger, as well as four firefighters, is suspected of operating on one of the company’s automated driving systems.

In February, NHTSA pressured Tesla into recalling nearly 363,000 vehicles with “Full Self-Driving” software because the system can break traffic laws. 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 light without proper caution or failing to respond to changes in speed limits.

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 2022, Tesla has issued 20 recalls, including several that were required by NHTSA.