The National Highway Traffic Safety Administration last August opened an investigation into Tesla's Autopilot driver-assist system, focused on crashes involving emergency vehicles when Autopilot was active. Now, it's upgrading that investigation, which brings the probe one step closer to becoming a possible recall.

NHTSA this week announced that it was upgrading its inquiry into approximately 830,000 Tesla vehicles equipped with Autopilot. In related documents published by NHTSA's Office of Defects Investigation, the government said it was taking this step "to extend the existing crash analysis, evaluate additional data sets, perform vehicle evaluations, and explore the degree to which Autopilot and associated Tesla systems may exacerbate human factors or behavioral safety risks by undermining the effectiveness of the driver's supervision."

The engineering analysis also brings in data from six additional incidents between November 2020 and January 2022, in addition to the 10 already under investigation. During this probe, NHTSA has reviewed more than 100 Tesla crashes involving both Autopilot and the automaker's Full Self Driving beta software. NHTSA also asked a dozen other automakers to submit data from their own SAE Level 2 systems.

From the data it's collected thus far, NHTSA noted in its investigation document that forward collision warnings activated "in the majority of incidents" just before impact, with automatic emergency braking engaging in roughly half of those collisions. NHTSA also noted that "Autopilot aborted vehicle control less than one second prior to the first impact" on average.

This brings NHTSA one step closer to the possibility of compelling Tesla to recall its vehicles, which include variants of the Model 3, Model S, Model X and Model Y sold between the 2014 and 2022 model years. Tesla could also initiate a voluntary recall if it so chose. The automaker does not operate a public relations team and thus could not be reached for comment.

Tesla is no stranger to government scrutiny outside this investigation. In early June, NHTSA asked Tesla to deliver data in regard to multiple reports of "phantom braking," where the vehicle will engage its brakes for seemingly no reason. Autopilot has also landed on the Federal Trade Commission's radar, with Reuters reporting that FTC Chair Lina Khan would neither confirm nor deny its own separate probe into Autopilot's efficacy, which could legally compel the automaker to change how it describes Autopilot's functionality to consumers.