TRAVERSE CITY, Mich. (AP) — Northern Michigan police say a woman whose body was found in a submerged minivan tested positive for several opioids and other drugs.

Traverse City police Capt. Keith Gillis said Friday that drowning has been ruled the cause of death of 22-year-old Morgan Victoria Fawn Elmer of Traverse City. A fisherman found the van in the Boardman River on Oct. 3.

Gillis says investigators believe Elmer may have driven the van into a parking lot at a boat launch, fell asleep and then mistakenly drove down the boat launch into the river.

Toxicology reports note Elmer tested positive for anti-anxiety and anti-seizure medication and multiple opioid painkillers.

Gillis said criminal charges are unlikely in the case.