NHTSA also investigated the 2016 crash and concluded that there was no "defect in design or performance" of the Autopilot system. An NTSB spokesman says the board sent two investigators.
In a post on Twitter, the federal safety agency said the "field investigation" would examine both driver and vehicle factors in Monday's accident.
A Tesla Model S reportedly on "Autopilot" smashed into the back of a fire truck parked at a freeway accident scene Monday morning, authorities said. It released a 500-page report past year that revealed former Navy SEAL Joshua Brown, 40, kept his hands off the wheel of his Tesla for extended periods of time despite warnings from the automated system.
The first fatality in a Tesla vehicle operating in Autopilot mode raised questions about the safety of systems that can perform driving tasks for long stretches with little or no human intervention, but which cannot completely replace human drivers. The Tesla S was apparently set in its self-driving mode and traveling at approximately 65 miles per hour when it ploughed right into the back of a big red fire truck owned by the Culver City Fire Department.
"Amazingly, there were no injuries", the department said.
Tesla wouldn't say if Autopilot was working at the time but says drivers must stay attentive when it's in use.
In the May 9, 2016 incident, driver Brown was shown to have switched the system on, but he also was found to have put his hands on the steering wheel for only 25 seconds during the 37.5 minutes that Autopilot was in operation. The company has repeatedly reminded drivers of this fact, as several drivers have blamed the Autopilot for accidents over the last couple of years.
Tesla shares are down 2.01% to $346.34 on Wednesday after reports that a Model S crashed into the rear of a fire truck while being controlled with the car's autopilot technology.
One of NTSB's key findings in the 2016 accident was that the Tesla automation system wasn't created to detect a truck crossing in front of it. The NTSB re-issued previous recommendations that the government require all new cars and trucks to be equipped with technology that wirelessly transmits the vehicles' location, speed, heading and other information to other vehicles in order to prevent collisions. But no auto company's technology as of the 2016 model year was "designed to brake for crossing path collisions".
The US National Transportation Safety Board is now gathering information about the accident, according to a Bloomberg report.
After the 2016 crash, the NTSB recommended automakers take additional steps to assuring that the driver is paying attention while using a driver-assist system.