Yosemite Park trail closed following the mysterious death of a family in August.
(CNN) -
Federal forestry officials have closed trails and campgrounds in a remote area near Yosemite National Park due to "unknown hazards" located in the area where a family and their dog were mysteriously found dead last month.
The bodies of Jonathan Gerrish, Ellen Chung, their 1-year-old daughter, Miju, and the family dog, Oksi, were found by search and rescue workers on August 17 in a remote area of the Sierra National Forest near the fork. south of the Merced River, according to the Mariposa County Sheriff's Office.
They were found on the Savage Lundy Trail.
The Sierra National Forest said it closed the area where the family was found as a precautionary measure due to "unknown hazards found on and around the Savage Lundy Trail."
Family found dead on hiking trail near Yosemite.
The authorities do not know what happened
"Designated recreation sites, roads and trails in the vicinity and / or leading to this location will be off limits to the public," the national forest said in a statement Saturday.
The closings are effective until September 26.
Since the closure was announced, the US Forest Service temporarily closed all national forests in California due to multiple wildfires burning in the state.
A "mysterious" crime
Investigators have yet to determine what caused the mysterious deaths.
Autopsies on the family and a necropsy on the dog were inconclusive, while toxicology results remain pending.
Some results could come as soon as Wednesday, Kristie Mitchell, a spokeswoman for the sheriff's office, told CNN.
The only potential causes of death that have been ruled out include gunshots or any other type of weapon, and chemical hazards specifically along the Savage Lundy Trail.
Detectives have not ruled out possible toxins in areas near the trail.
Warning signs of a toxic algal bloom have been posted in the area since mid-July along the southern fork of the Merced River, in the vicinity of where the family was found.
The water samples from the area, along with samples of the drinking water that the family packed, were sent to laboratories for analysis.
Search warrants for the family's home and cars did not yield significant evidence.
Their phones have been harvested and are being mined by the FBI.
"We know that John and Ellen's family and friends are desperate for answers, our detective team is working around the clock," Mariposa County Sheriff Jeremy Briese said in a statement.
"Cases like this require us to be methodical and thorough while using whatever resources we can find to help us provide those answers as quickly as possible."
The family was generous, amazing, says a friend
Steve Jeffe said he met the couple in San Francisco years ago and they became very close after each moved to the Mariposa area.
"They were amazing people, very generous," Jeffe told CNN.
"They love their daughter very much."
Gerrish worked for Google and had recently started working on Snapchat, according to Jeffe, who was tipped off by friends after the family didn't come home after a day of hiking last month.
This is what the "waterfall of fire" phenomenon looks like in Yosemite National Park
The family's babysitter found no one home when she arrived Monday morning, and after Gerrish failed to show up for work, "the alarms sounded," Jeffe said.
"They were an incredibly caring and loving family," said Jeffe, who described the couple as loving with a very large group of friends.
"It's a puzzling event. There is something very puzzling about what happened," Jeffe said.
"Whether environmental or man-made, it was obviously something they found," added Jeffe, speculating on what may have led to their deaths.
Mitchell said the area where the family was found is popular in the spring because of its colorful wildflowers and it is very hot this time of year with little shade.
He said the family was well prepared for a day hike.
- David Williams of CNN contributed to this report.
CrimeYosemite National Park