A Tesla Model S driver smashed into the back of a parked firetruck Monday morning, according to California fire officials, and claims the car was in its semi-autonomous Autopilot mode when it happened.

The car hit a truck around 8:30 a.m. Monday on Interstate 405 in Culver City, according to the union representing firefighters in the city.

“Amazingly there were no injuries!” the union said on Twitter. “Please stay alert while driving!”

The California Highway Patrol and Culver City Fire Department that a Tesla hit a fire truck, but neither could say whether the vehicle had been on Autopilot. The fire truck was situated in the left emergency lane, blocking the scene of a previous accident, the newspaper reported, when the Tesla-involved crash occurred.

When reached Tuesday morning by Jalopnik, a Tesla spokesperson reiterated the company’s official line on Autopilot.

“Autopilot is intended for use only with a fully attentive driver,” a Tesla spokesperson said.

Autopilot is a suite of advanced driving assistance features, including adaptive cruise control and Autosteer, which keeps the car driving within a lane. It’s unclear if the car slowed down before the crash.

Culver City Fire Department battalion chief Ken Powell told the Mercury News the Model S suffered significant damage. Luckily, no firefighters were at the rear of the vehicle at the time of the crash. From the Mercury News:

Had any firefighters been at the rear of the truck rather than in front attending to the earlier crash, there “probably would not have been a very good outcome,” Powell said.

“It was a pretty big hit,” Powell said.

The Tesla driver refused medical attention, the newspaper reported.

Tesla’s automated driving features have been in the news time and again since mid-2016, after getting in an accident while his car was traveling in Autopilot. In part, the driver for relying too much on Autopilot, as well as Tesla for allowing the feature to be used on roads that may not be suitable for automated driving.

We say it often, but again: if you do in fact use driver aids like this, please, please, pay attention to the road.

The NTSB has weighed in and said it’s now gathering information about the crash, :

The U.S. is gathering information about an accident involving a Model S sedan that rear-ended a firetruck on a freeway near Los Angeles on Monday, the agency said.

The safety agency has not yet decided whether it will open a formal investigation of the crash, NTSB spokesman Chris O’Neil said in an email.

Now, an official investigation is underway, America’s top auto regulator is also getting involved, :