Tesla Motors told U.S. Senate Commerce Committee staff it is considering two theories that may explain what led to the May 7 fatal crash that killed a Florida man who was using car’s “Autopilot” system, a person familiar with the meeting told Reuters on Friday.
Tesla (TSLA) staff members told congressional aides at a briefing Thursday they are still trying to understand the “system failure” that led to the crash, the source said.
Get Data Sheet, Fortune’s technology newsletter.
Tesla is considering whether the radar and camera input for the vehicle’s automatic emergency braking system failed to detect the trailer or the automatic braking system’s radar may have detected the trailer but discounted this input as part of a design to “tune out” structures such as bridges to avoid triggering false braking events, the source said.
For more about Tesla’s Autopilot system, watch:
A Tesla spokeswoman declined to comment on the meeting, referring questions to the company’s recent statements.