Zion National Park

In this Monday, July 22, 2013, file photo, hikers look up at a fast moving storm as it makes its way through Zion National Park outside of Springdale, Utah. 

SALT LAKE CITY — Toxic levels of a cyanobacteria have been detected in a Utah river for the first time after a dog suffered seizures and died at Zion National Park, officials said.

Public health officials have since cautioned people against swimming or letting their animals enter the Virgin River's North Fork, which flows out of the park and through several towns.

The dog died July 4, an hour after clawing at and ingesting the algae in the river, according to park spokesman Jeff Axel.

“When the dog was pawing at the rocks, it freed up the toxins from the bacterial mat,” he said.

Most communities have stopped using the river as a source of drinking water since the dog died.

In response to the dog’s death, samples were taken along the river and brought to Salt Lake City for testing. The results indicated concentrations of anatoxin-a, the harmful substance produced by cyanobacteria that affects the nervous system at nearly four times the health threshold for recreational exposure, the Salt Lake Tribune reported.

The harmful algae was found in multiple spots in the river.

The state has previously issued health warnings for E. coli impairment in the North Fork.

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