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       A Northern California family and their dog who were mysteriously found dead in a remote hiking area most likely died from hyperthermia and probable dehydration, authorities said Thursday.

       The Mariposa County Sheriff's Office previously said the updates on the deaths of John Gerrish, wife Ellen Chung, their 1-year-old daughter Miju, and their dog Oski, an 8-year-old Aussie/akita mix, would be the final investigative update on the case.

       CALIFORNIA AUTHORITIES TURN TO CELLPHONE DATA AND SOCIAL MEDIA IN MYSTERIOUS DEATHS OF FAMILY

       John Gerrish and Ellen Chung had recently moved to the Marisopa area with their 1-year-old daughter and dog. The family and dog all died of extreme heat and dehydration, authorities said Thursday. (Steven Jeffe)

       The family was found dead on Aug. 17 on the Savage Lundy Trail near the Merced River in the Sierra National Forest. A friend had reported them missing after Gerrish, a software engineer who formerly worked at Google, failed to report for work.

       The area where they were hiking had temperatures between 107 degrees and 109 degrees at one point and there was little shade, Mariposa County Sheriff Jeremy Briese said.

       "This is, again, an unfortunate and tragic event due to the weather," he said. "Heat-related deaths are extremely difficult to investigate."

       Gerrish and Chung were wearing shorts and tank top attire on the hike and their water container was empty, he said. They were found more than 1.5 miles from their vehicle.

       The hiking trail map shows where the Geriish family was found dead in August. (Mariposa County Sheriff's Office)

       In a statement from the Gerrish-Chung families, they said the loss of their loved ones was exacerbated by the death of a young child.

       "The question ‘Why?’ can never be answered and will remain with us," the family said. "Our hearts will never forget the beautiful lives of Jonathan, Ellen, Miju and, of course, Oski. They will remain with us wherever we go and in whatever we do."

       The deaths stumped investigators as foul play was ruled out. The bodies had no signs of wounds or trauma, authorities said at the time.

       High levels of toxic algae in the river was one theory investigated. In July, the California Department of Fish and Wildlife warned that "water testing along the Merced River near Hites Cove … show[s] a high concentration of algae bloom."

       Other possible causes that were thought to have been responsible for the deaths were toxic gases in the area.

       The deaths led the Bureau of Land Management to close campgrounds and recreation areas along 28 miles of the river, between the towns of Briceburg and Bagby, when water samples downstream from where the family died showed high levels of toxic algae.

       Sierra National Forest. A Northern California family and their dog were found dead on a hiking trial in the forest. (U.S Department of Agriculture, Forest Service)

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       Autopsies performed on the family and a dog necropsy were deemed inconclusive. Investigators have worked with toxicologists, environmental specialists and other experts.

       The Associated Press contributed to this report.