Officials narrow cause of death for California family found on hike near Yosemite

But notably, they have not ruled out toxic algal blooms. Testing conducted earlier this month confirmed that the nearby Merced River had high levels of toxic algae.  And while Arizona State University professor Taylor Weiss previously told SFGATE that “finding evidence of that poisoning will be very challenging,” it has yet to be fully ruled out. A portion of the Merced River near where the family died was closed earlier this month because of the toxic algae, while the Savage-Lundy Trail reopened Sunday after being closed due to “unknown hazards.” They also have yet to rule out extreme heat. The temperature at the time, according to the sheriff’s office, ranged from 103 to 109 degrees.

Previous autopsy data provided by the Mariposa County Sheriff’s Office has ruled out chemical hazards on the Savage Lundy Trail and acute trauma, such as stabbing, gunshot wounds or blunt-force trauma. Mariposa County Sheriff’s Office spokesperson Kristie Mitchell told SFGATE earlier this month that results from several toxicology reports are still pending, and as of Wednesday “a few key reports” have yet to be obtained, according to a statement. (A spokesperson did not immediately respond to a request for comment from SFGATE Wednesday.) It also remains unclear what happened to cell phone and social media records obtained by investigators. Detectives with the Sheriff’s Office are continuing to investigate with a team of toxicologists, environmental specialists and the FBI, among others, they said in a Wednesday statement. Their death is still being handled as a hazmat and coroner investigation. “We respect and understand the need for information and details regarding this case. Our current priorities remain supporting and informing the Gerrish / Chung family during this tragic time,” said Mariposa County Sheriff Jeremy Briese in a statement. “As we navigate through this investigation with the family, we will later share our findings with the public.” SFGATE California Parks editor Ashley Harrell contributed to this report.