WASHINGTON COUNTY, Utah (ABC4) — Harmful algae mats in the Virgin River have left one dog dead and three others sick, causing the Utah Dept. of Environmental Quality to issue a Health Watch.

The dogs reportedly became ill after exposure to water in the Virgin River in St. George, Bloomington, and Hurricane. The reports caused the DEQ to issue a Health Watch for the lower Virgin River.

Harmful algae mats, also known as benthic cyanobacteria, often have a “mucousy, gelatinous texture” and can be green, blue, yellow, or brown, a release states. “They are often toxic and can be found growing on submerged rocks, plants, river banks, and sand, or as floating mats in lakes, reservoirs, and rivers.”

Humans and animals alike are exposed to the toxins when they either ingest algae mat material or drink water in areas containing the harmful algae, DEQ officials say. Dogs are reportedly attracted to the smell of the mats, so pet owners should beware.

Additionally, dogs are most at risk for lethal exposure, the release states.

Symptoms most commonly reported in pets after exposure to “anatoxin-a” include excessive drooling, stumbling or muscle tremors, difficulty breathing, weakness, seizures, paralysis, and death.

Symptoms begin quickly, officials say, beginning minutes or hours after exposure.

If harmful algae are present in water in your area, do not let your pets drink the water, swim in the water, eat near the water, eat algae or algae mats, or eat dead animals, such as fish, found near the water.

If your pet goes in the water, officials say to rinse them off immediately and do not let them lick their fur.

“Prevention is the best way to protect pets. If you believe your pet was exposed to a harmful algae mat, seek immediate care from your veterinarian,” the release states.

To check conditions before visiting a waterbody, or to learn more about harmful algae mats, visit the DEQ’s website here.