After the disappearance and unexplained deaths of a Northern California family of three and their family dog, investigators are now searching for clues in a remote area of the Sierra national forest.

According to The Guardian, San Francisco-based software designer John Gerrish, his wife, Ellen Chung, their one-year-old daughter, Muji, and their dog were found dead in Mariposa county's hiking trail on Tuesday. A family friend reported that they were missing Monday evening.

Unsolved Deaths of California Family

Based on the investigation crews that had searched the area, they located the family's vehicle near a gate to the Sierra national forest on Tuesday. During their search, they have found the bodies of the family members and the dog just a little over a mile away. The said hiking trail, which is a remote area, had no cellphone service.

Kristie Mitchell, a spokesperson with the Mariposa County sheriff's office, said Thursday that the cause of death of the family members and their dog remained unclear. Mitchell added that they had not ruled anything out yet.

The sheriff's office was currently investigating the deaths along with the California Department of Justice. Sheriff Jeremy Briese said that this was never the outcome they wanted or the news they wanted to deliver. Briese added that his heart breaks for their family. 

Briese also said that Sheriff's Chaplains and staff were working with their families and would continue to support them during this heartbreaking time.

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California Mine Turned into Hazmat Site?

According to CBS News, Briese said there were some abandoned mine shafts in the area, which could release dangerous gases. However, this has not yet been ruled as a determining factor. 

Briese said they had not located a mine nearby. But in their initial investigation, they suspected that it was mine in the area.

Briese clarified that they were taking the investigation slow and methodical for the safety of their rescuers as well. The sheriff said the trail, where the family was on, had warnings about toxic algal blooms in the Merced River. 

However, authorities said it was still too early in the investigation to determine if that possibly impacted the family during their hike.

On Wednesday, investigators noted that the area where the family was found was briefly treated as a hazmat site. Investigators were exploring whether there was carbon monoxide or they were exposed to gas from mines in the area. They added that toxic algae also could have been responsible for the tragedy.

A family friend, Sidney Radanovich, a Mariposa real estate agent, said Gerrish, a San Francisco-based software designer, fell in love with the Mariposa area. 

Radanovich noted that Gerrish already bought several homes there. He added that the Gerrishes were avid hikers. 

"They were such a loving couple, they loved each other quite a bit," Radanovich said.

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Written by: Jess Smith

WATCH: Family of 3 Found Dead in Remote California Hiking Area - From CBS News