National Park Service (NPS) officials issued a water advisory for Lake Powell just before the July 4 holiday weekend after toxins produced by certain algae were detected. The alert urged boaters and visitors to use caution and avoid unnecessary exposure to the water, as the toxins present may be harmful to both humans and animals.

The concentration of cyanotoxins was found to be at the “high end of safe exposure levels” in the Antelope Canyon portion of the reservoir, which straddles the Utah-Arizona border, according to Glen Canyon National Recreation Area officials, who warned visitors on Wednesday.

Levels of cyanotoxins that were on the "high end of safe exposure levels" were observed at the mouth of Antelope Canyon in Lake Powell.