Three young sisters who were found dead near a Washington campground after they left home for a "planned visitation" with their father died from suffocation, authorities said Monday.

Paityn Decker, 9; Evelyn Decker, 8; and Olivia Decker, 5, were located on June 2 near the Rock Island Campground in Chelan County, Washington, following a search, police said.

This undated photo provided by Whitney Decker shows Paityn, Olivia and Evelyn Decker. Courtesy of Whitney Decker via AP

An autopsy completed on Friday determined the girls' cause of death to be suffocation and the manner of death is homicide, according to the Chelan County Sheriff's Office.

The girls had each been found with plastic bags over their heads and their wrists were zip-tied, according to court documents previously o

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