Sheriff's Cmdr. Steve Aust says coworkers of the 50-year-old woman found the bodies Tuesday after she didn't show up for work. Aust says the woman and the 60-year-old man found with her were related and lived in the home. Their names were not immediately released.
The sheriff's officer says there was no sign of forced entry and "no obvious signs of lethal injury."
Autopsies are scheduled for Thursday.
Aust says the sheriff's office is assisting Napavine police.
Napavine is about 75 miles south of Seattle.