The Cowlitz County coroner says a Longview, Wash., dentist found dead in January at a southwest Washington Interstate 5 rest stop died of a morphine overdose.

The Daily News of Longview reports Coroner Tim Davidson said Wednesday that William Lesh's death was accidental. Davidson says while the 44-year-old man also had some underlying natural disease processes, they did not factor into his death.

Lesh was found dead Jan. 22 at a rest stop north of Castle Rock. The Cowlitz County sheriff's office says the man was lying on the ground outside his gray BMW with a bump on his head.