An autopsy on a woman who died in Lake Brantley on Friday showed she was the victim of a drowning.

Story Waggoner, 20, was out with some friends swimming from a boat after some late-night partying, when she slipped away from her friends a little before 5 a.m. Her body was found more than five hours later.

The autopsy confirmed that she drowned, but it also said she had elevated levels of carbon monoxide in her system.

Investigators said that is consistent with swimming behind a boat with the engine running, and they said they don't know if it contributed to her death.

Toxicology reports are not expected for a number of weeks.