No "safety-related defect" was identified in May's crash on a Florida highway, National Highway Traffic Safety Administration spokesman Bryan Thomas told reporters.
"The investigation is closed," he said.
The NHTSA also looked at dozens of other non-fatal crashes that happened when the Autopilot feature was in use in Teslas, including the Model S involved in the fatal crash, Thomas told reporters in a conference call.
While no defect is apparent in the overall system or the Automatic Emergency Braking feature, and no further investigation is needed for now, "the closing of this investigation does not constitute a finding by NHTSA that no safety-related defect exists," he said.
"The agency will monitor the issue and reserves the right to take future action if warranted by the circumstances."
Tesla founder Elon Musk tweeted shortly after the NHTSA finding was announced, calling the final report "very positive."
Thomas said the investigation indicated the fatal Florida crash, in which a Tesla was hit by a truck crossing a highway, involved "a number of human factor issues," including use of the automatic system beyond its design.
