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 ; ).