The National Transportation Safety Board (NTSB) has opened an investigation into a crash that happened over the weekend in Texas, in which a driver slammed into a home in Katy, Texas, killing a resident.

The family of that victim, 76-year-old Martha Avila, has also filed a lawsuit against the driver, Michael Butler, and Tesla, alleging negligence.

The NTSB joins the National Highway Traffic Safety Administration (NHTSA) in investigating the crash. While Butler allegedly told local authorities that he was using Tesla’s Autopilot feature before the crash, the company has since said it has data showing that Butler’s accelerator pedal was pressed to the floor. This “overrode” what was more likely the Full Self-Driving software on his car, pushing his speed to 73 miles per hour before he hit the house, according to Tesla.

Tesla has not provided more proof beyond those statements, though. The NTSB and NHTSA investigations will likely require the company to turn over logs created by the car’s onboard computers that will ultimately reveal how exactly the crash happened.