A family of three died of hyperthermia and probable dehydration while hiking in a remote area in California this summer, Mariposa County Sheriff Jeremy Briese announced Thursday. Their dog was also with them, and officials believe it died of a probable heat-related death. 

"This is a real tragedy," Briese said Thursday. 

On August 17, John Gerrish and Ellen Chung and their one-year-old-daughter Miju were found dead in the Devil's Gulch area of the Sierra National Forest a day after a family friend reported them missing. Their dog was also found dead, officials said.

Temperatures on the day of the hike ranged from 92 degrees to approximately 103 degrees Fahrenheit, Briese said. Hyperthermia, which is another form of heat stroke, is when the human body reaches an abnormally high body temperature, according to the National Institutes of Health. 

Briese said their one water container was found empty, and no additional water or filtration systems were located. There was no evidence of any portable dog bowls.

Upon finding the bodies in August, authorities treated the area as a hazmat scene since there was no clear cause of death. The remote area where the bodies were found had no cellphone service, had warnings about toxic algal blooms in the Merced River and was near abandoned mine shafts that potentially could have release dangerous gases, officials said. 

"This is a very unusual, unique situation," Kristie Mitchell, a spokesperson for the sheriff's office said in August, according to CBS San Francisco. "There were no signs of trauma, no obvious cause of death. There was no suicide note."

Briese said there was no evidence that the family drank any of the water in the Merced River, which was confirmed to have toxins in it. He also said that there was no evidence that the family located or used the abandoned mine shafts in the area. 

Several sites and trails in the Sierra National Forest were closed due to public safety and "unknown hazards" following the family's deaths. 

The California Department of Justice assisted in the investigation.