An underwear-clad pedestrian who was killed Monday morning as she crawled on a San Francisco freeway has been identified, but the situation behind her strange death remains a mystery.

California Highway Patrol spokesperson Sergeant John Cardoso said Monday that calls reporting a pedestrian "crawling on the freeway in underwear" began to roll in at 6:18 a.m.. By 6:20, the pedestrian had been fatally struck in the southbound lanes of 280 near Alemany Boulevard, Cardoso says.

According to Bay City News, the pedestrian, who was identified Wednesday by the San Francisco Medical Examiner as 23-year-old Alexandra Stevenson, "was struck by more than one vehicle" as she crawled "in the lanes of traffic," but none of the drivers who hit her stopped at the scene.

Cardoso said Monday that it was unclear why Stevenson, who had no known address, was on the freeway. That mystery remains today, as CHP spokesperson Officer Vu Williams told Bay City News that investigators still don't know "why Stevenson was in the roadway or how she got there," but hope that toxicology reports "might shed light on whether drugs or alcohol played a role."

If you know anything about the collision or Stevenson, Williams hopes you will assist the investigation by calling CHP San Francisco at (415) 557-1094, or the CHP’s non-emergency public access number (800) TELL-CHP.

Previously: Underwear-Clad Pedestrian Killed While Crawling On San Francisco Freeway