Interesting! I guess I really don't know anything about forensic pathology. But I do hope they can unravel the mystery! If for no other reason than to prevent further loss of life.

More food for thought. When you do a hike like they were attempting and you know you have a 2,500 ft climb out, you stock up with water before leaving the river. Other things that may mean they did not drink the water are (hence no toxins to be found in their system)...

1. Little water left for water testing when found.
2. Authorities already saying one positive test was found downstream but no mention of the result of water with family..prob negative
3. Now looking for other things like lightning.

Yes, I could be a little obsessive on this case ; ).

An account of someone else surviving an algae bloom.

https://www.wral.com/jared-lloyd-firsthand-experience-with-an-algal-bloom/19869971/

Seems Anatoxin-a (aka Very Fast Death Factor) was the toxin found in high levels where the family was.

Still no confirmation though.

Interesting!

The positive test in an algal mat for Anatoxin-A (ATX) downstream from the found family was 11.8 µg/L. Algal mats can be positive for 1,000s of units, so that level is low, not high as the media states.
https://mywaterquality.ca.gov/habs/where/freshwater_events.html

The WHO, in their Guidelines on Recreational Water Quality, 2021, gives a WHO guideline value (GV)recreation for Anatoxin A at a level of WHO HBVrecreation = 60 µg/L
(For ATXs, toxicological data were insufficient for deriving a guideline value, but allow deriving an upper bounding value below which health impacts are highly unlikely – that is, a health-based value.)
https://www.ncbi.nlm.nih.gov/books/NBK572631/

Some municipal waters allow ATX at levels of 20 µg/L (Ohio at that level only puts out advisory)
https://en.wikipedia.org/wiki/Anatoxin-a

Few more details, they had a CamelBak.
Anatoxin-A cannot be filtered out of water, and they didn't have one anyway.

https://www.sfgate.com/bayarea/article/toxic-algae-california-family-death-yosemite-16461960.php

6 More Causes of Death Ruled Out for Calif. Family Who Mysteriously Died on Hiking Trail

https://www.yahoo.com/entertainment/6-more-causes-death-ruled-235753599.html

My top scenario is they took all the water from the start (knew they could not use river water), the 1 year old started showing signs of heat stress at the bottom (under age 4 are extremely vulnerable) and they panic-hiked to get out.

Dutch news article.

https://panorama.nl/artikel/459798/amerika-is-een-mysterie-rijker-was-het-dan-toch-de-hond

Translation of the last sentence, only thing haven't read before.

"The most plausible explanation so far is that the dog inadvertently killed itself and its owners by walking into a river with toxic blue-green algae and then shaking itself dry."

*Dutch website.