Tesla Motors told U.S. Senate Commerce Committee staff it is considering two theories that may help explain what led to the May 7 fatal crash that killed a Florida man who was using the car's "Autopilot" system, a person familiar with the meeting told Reuters on Friday.

Tesla staff members told congressional aides at an hour-long briefing on Thursday that they were still trying to understand the "system failure" that led to the crash, the source said.