The mystery of the cause of death of an American family who died with their dog while hiking through the Sierra National Forest in California has been solved.

More than two months after the bodies of software engineer John Gerrish, his partner Ellen Chung, and their one-year-old daughter Miju were found, the Mariposa District Sheriff announced Thursday that the family had become overheated, possibly related to dehydration, was killed.

The case had caused speculation in the United States for weeks, as the family's eight-year-old Akita was also found dead.

Gerrish and Chung, who were considered experienced hikers, had set out on the morning of August 16 with their daughter and dog at about 23 degrees for the Hites Cove Trail.

The temperatures in the region later rose to almost 43 degrees.

Since the bodies showed no injuries and no drugs or drugs were found in toxicological examinations, the judicial authorities began looking for possible toxins in algae or the forest floor.

In September, the trail was temporarily closed due to "unknown dangers".