A family of 3 and their dog were found dead on a hiking trail in Northern California. Officials have no idea what happened.

• A family of three and their dog went missing while hiking in Sierra National Forest this week.
• After they were reported missing, officials found the bodies on a trail, with no clear cause of death.
• The country sheriff said he's "never seen a death like this" and the area is being treated as a hazmat site.

Officials are mystified after a family of three and their pet dog were found dead on a hiking trail in Northern California earlier this week.

The bodies of John Gerrish, Ellen Chung, their 1-year-old daughter, Miju, and their dog were found Tuesday in the Jerseydale area near Yosemite National Park, the Mariposa County Sheriff's Office said.

The sheriff's office began a search and rescue operation after someone reported the family missing at around 11 p.m. on Monday. The search team first located the family's car near the Hites Cove area of the Sierra National Forest. The bodies were found shortly after, around 11 a.m., near the Devil's Gulch area.

"This is never the outcome we want or the news we want to deliver, my heart breaks for their family. Our Sheriff's Chaplains and staff are working with their family and will continue to support them during this heartbreaking time." Sheriff Jeremy Briese said in a statement.

There was no obvious cause of death and no signs of blunt-force trauma. Briese told KSEE that this was the first incident like this he had seen in his 20 years on the job.

"I've worked in different capacities but I've never seen a death like this," Briese said.

Kristie Mitchell, a spokesperson for the Mariposa County Sheriff's Office, told the San Francisco Chronicle the case was a "very unusual, unique situation."

"There were no signs of trauma, no obvious cause of death. There was no suicide note. They were out in the middle of a national forest on a day hike," she said.

The sheriff's office is investigating with assistance from the California Department of Justice.

While officials wait for the autopsies and toxicology results to be completed, the area in which the bodies were found is being treated as a hazmat site.

Mitchell told the Chronicle investigators are looking into the possibility that the family was exposed to toxic algae or toxic gas from nearby mines.

Briese told KSEE there were some warnings about toxic algae blooms in the river near the trail where the bodies were found, but it's not yet clear if there was a connection to the deaths.

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