The National Traffic Highway Safety Administration has opened an investigation into a fatal crash involving a Tesla, according to documents viewed by TechCrunch.

The investigation, which was opened in July, is the latest in a long string of inquiries by NHTSA’s Special Investigations program into crashes involving Tesla vehicles. This fatal crash, in which a pedestrian was killed, involved a 2018 Tesla Model 3 in California.

NHTSA’s special crash investigations program focuses on cases useful for examining special crash circumstances or outcomes from an engineering perspective. The agency currently has 45 open SCI cases involving advanced driver assistance systems or automated driving. Of those, 36 involve Tesla vehicles. Eleven of the Tesla crashes resulted in 15 fatalities.

Tesla’s advanced driver assistance system known as Autopilot has increasingly come under scrutiny by the federal agency. Last month, NHTSA  “upgraded” its investigation into Tesla’s Autopilot  after discovering new incidents of the EVs crashing into parked first-responder vehicles.

The agency said in a notice  that it was expanding its preliminary evaluation of Tesla Autopilot systems to an engineering analysis. This means that NHTSA will extend its existing crash analysis, evaluate additional data sets and perform vehicle evaluations as well as evaluate whether Autopilot and associated Tesla systems may exacerbate human factors or behavioral safety risks by undermining the effectiveness of the driver’s supervision, according to the agency.

The escalation is a critical and required step before NHTSA can issue a recall. An estimated 830,000 Tesla vehicles are involved in the probe, according to agency documents.