The U.S. highway safety agency will send teams to investigate two November crashes involving Teslas with automated driving systems.
Since 2016, the NHTSA has investigated 35 crashes involving Tesla's "Full Self-Driving" or "Autopilot" systems. In the crashes, 19 died.
On Thanksgiving, eight vehicles crashed on the San Francisco-Oakland Bay Bridge. The driver told authorities his Tesla Model S was using "Full Self-Driving" software.
The eight-vehicle crash closed two lanes and snarled holiday traffic. One child was hospitalized for minor injuries.
A Tesla Model 3 crashed into an Ohio Highway Patrol SUV with flashing emergency lights near Toledo on Nov. 18.
In the crash near Toledo, an Ohio State Highway Patrol trooper and another driver were injured when a Tesla Model 3 hit the police SUV's emergency lights.
A message was left Thursday seeking Tesla's response to the latest NHTSA action. The company, based in Austin, Texas, has disbanded its media relations department.
Since 2006 and a half, the NHTSA has been conducting an investigation into Tesla's automated systems without taking any enforcement action.