U.S. safety regulators are turning up the heat on Tesla, announcing investigations into steering wheels coming off some SUVs and a fatal crash involving a Tesla suspected of using an automated driving system when it ran into a parked firetruck in California.

The National Highway Traffic Safety Administration said Wednesday it is launching a special crash-investigation team to probe the Feb. 18 crash involving a Tesla Model S and a ladder truck from the Contra Costa County fire department.

The firetruck probe is part of a larger investigation by the agency into multiple instances of Teslas using the automaker’s Autopilot system crashing into parked emergency vehicles that are tending to other crashes. NHTSA has become more aggressive in pursuing safety problems with Teslas in the past year, announcing multiple recalls and investigations.

The driver of the 2014 Tesla Model S was killed in the crash and a passenger critically injured. Four firefighters were treated for minor injuries, and the $1.4 million ladder truck was damaged.

NHTSA is investigating how the Autopilot system detects and responds to emergency vehicles parked on highways. At least 14 Teslas have crashed into emergency vehicles nationwide while using the system.

Automated driving systems aren't always involved in the crashes that NHTSA sends investigators to. For instance, the Ohio State Highway Patrol determined that a Tesla that hit one of its patrol cars in November was not operating on "any type of autonomous mode.”

Authorities said the California firetruck had its lights on and was parked diagonally on a highway to protect responders to an earlier accident that did not result in injuries.

Lewis Broschard III, chief of the Contra Costa County Fire Protection District, said his department is concerned about the risks that inattentive drivers pose to themselves, passengers and first responders.

“These unnecessary deaths, injuries, risks to firefighters, and loss of valuable equipment are all preventable," he said, urging drivers to slow down and move over for emergency vehicles.

“Recent reports of automobiles that may have been operating automated driving systems crashing into parked emergency vehicles at the scene of an emergency is a serious concern for the safety of our firefighters and paramedics and the public we are serving,” Rob Brown Jr., CEO of the International Association of Fire Chiefs, said in an email.

A NHTSA spokeswoman said she couldn't comment on an open investigation when asked if the Teslas are posing a danger to emergency workers.

NHTSA has been scrutinizing Teslas more intensely in the past year, seeking several recalls and opening investigations.

Earlier Wednesday, the agency posted documents revealing an investigation of steering wheels that can detach from the steering column on as many as 120,000 Model Y SUVs.

The agency said it received two complaints in which 2023 Model Ys were delivered to customers with a missing bolt holding the wheel to the steering column. A friction fit held the steering wheels on, but they separated when force was exerted as the SUVs were driven.

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

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 he was able to pull toward the road divider. There were no injuries.

It was a "horrible experience," the car's owner, Prerak Patel, told The Associated Press. He said he was in the freeway's left lane when the steering wheel came off and was lucky the road was straight and he was able to stop the car at the divider.

Messages were left seeking comment from Tesla, which is based in Austin, Texas.

At first a Tesla service center gave Patel 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 Patel wrote that he had lost faith in Tesla and asked for a refund, the service center removed the charge.

Patel was later given the option of keeping the car or getting it replaced with a new one. Patel said he chose a replacement.

Patel said he's a fan of Tesla CEO Elon Musk and has invested a large chunk of his savings in Tesla stock, which closed Wednesday down 3%.

“My kids were a little scared to ride in a loaner Tesla and, as a parent, we are able to restore their confidence,” Patel said. He said he hopes Tesla will investigate and improve its quality control.

Detached steering wheels are rare in the industry, but not unprecedented. In February, Nissan recalled about 1,000 Ariya electric vehicles for a similar problem.

NHTSA also has opened investigations during the past three years into Teslas braking suddenly for no reason, suspension problems and other issues.

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 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 from a turn-only lane, going through a yellow traffic light without proper caution or failing to respond to speed limit changes.

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

Tesla says in its owners manual that neither Autopilot nor “Full Self-Driving” can drive themselves, and that owners must be ready to intervene at all times.

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.