The conductor of a San Francisco train that in 2021 dragged to death a woman was cleared of wrongdoing by federal investigators, according to a report made public Tuesday.

Amy Adams, 41, had boarded a Bay Area Rapid Transit train at the Powell Station with her dog tethered to her waist by a leash. As the doors were closing, she stepped out, but the dog stayed on the train. The train took off, and Adams was dragged and pulled onto the tracks and killed on Sept. 13, 2021. The dog was not injured, BART officials said.

Adams appeared to be waving at someone moments before the train started moving, they said. A witness told KGO-TV that he saw the woman being dragged and a man who was hysterical on the platform who told him the woman killed was his girlfriend.

The National Transportation Safety Board said the train conductor followed BART’s procedures that required him to look for passengers before departing a station but did not see Adams, who was more than 600 feet (180 meters) away from him, or the dog leash trapped between the doors.

The NTSB said dim lighting at the station “likely made it difficult for the train operator to reliably monitor and evaluate passengers exiting and entering the rear of the train.”

BART has since completed lighting and painting improvements at the Powell Street Station and other nearby stations to improve visibility for its train conductors, the agency said.

Toxicology tests on the train conductor didn't identify any illicit substances, it said.

Adams tested positive for methamphetamine, cocaine and fentanyl in an autopsy conducted by San Francisco authorities, the agency said.

“It is likely that the passenger was experiencing at least some impairing effects of substance use at the time of the accident,” the NTSB said, adding that investigators found no clear evidence that impairment played a role in the accident.