The National Highway Traffic and Safety Administration (NHTSA) revealed Thursday that the U.S. automotive safety regulator is seeking an updated response and current data from Tesla (NASDAQ:TSLA) regarding an ongoing probe into 830,000 Tesla vehicles and the automaker’s Full Self-Driving system (FSD).

The NHTSA sent a letter to Tesla on July 3rd seeking updates to questions it had asked in August 2022. According to a copy of the letter made public by the agency, the regulator is now demanding answers by July 19th.

The agency is currently conducting an investigation into the functionality of Autopilot following the identification of over a dozen incidents where Tesla vehicles collided with stationary emergency vehicles. Additionally, the investigation aims to determine if Tesla vehicles effectively ensure that drivers remain attentive while utilizing the driver assistance system.

Autopilot is designed to enable vehicles to autonomously steer, accelerate, and brake within their designated lane, while enhanced Autopilot can assist in lane changes specifically on highways. It’s important to note that Tesla’s FSD Capability Features allow vehicles to obey traffic signals and stop signs, but they do not render the vehicles fully autonomous.

The agency said in 2022 nine of 11 vehicles in prior crashes exhibited no driver engagement, or visual or chime alerts, until the last minute preceding a collision, while four showed no visual or chime alerts at all during the final Autopilot use cycle.

The letter asks for updates on all Tesla changes related to driver engagement or attentiveness.

Since 2016, the NHTSA has initiated 40 special crash investigations involving Tesla vehicles, focusing on incidents where advanced driver assistance systems like FSD were potentially engaged. Among these investigations, there have been reports of 20 fatalities related to the crashes.

Shares of TSLA are down 1.48% in premarket trading on Thursday.