PIERRE, S.D. (AP) — Authorities in central South Dakota say preliminary results from an autopsy indicate that foul play was not a factor in the death of a woman whose body was found in the Missouri River earlier this month.

Fifty-six-year-old Carol Olson was last seen Nov. 3, and six days later, a man walking his dog near the Stanley County fairgrounds found her body in the river.

Stanley County Coroner Gary Grittner says the autopsy showed that Olson died from drowning. He says her body had no injuries that would indicate that someone killed her.

Grittner says final autopsy results won't be ready until toxicology reports are completed, which could take a few months.

Officials said earlier that Olson, of Pierre, had health issues and might have been without her medication.

Copyright 2015 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

More From KXRB