PORTLAND, Ore. (KOIN) — Washington County officials say swimmers are free to continue diving into Hagg Lake after its water tested negative for toxic cyanobacteria

The Oregon Health Authority collected water samples on July 15 from five separate locations around the lake after a family pet died shortly after swimming in the lake. 

All water samples came back negative for cyanobacteria. 

OHA says these test results are encouraging and people can continue to swim in the lake, but they should use caution and keep an eye out for signs of a “bloom.”

“It can look like a thick foam or a scum on the surface. They can be different colors. They can be green or bluish green,” said Curtis Cude, who manages some of the public environmental health programs at Oregon Health Authority. He said the bacteria can also appear white or brown and can give off an odor. 

Although often referred to as algae, cyanobacteria are actually bacteria that are naturally found in fresh and salt water around the world. They help sustain oxygen levels in the atmosphere. However, warm weather conditions can cause the bacteria to multiply quickly and that’s when they can be harmful to humans and pets. 

People or pets can become sick if they swallow water with cyanotoxins. Symptoms from cyanotoxin poisoning often mimic those of food poisoning: stomach cramps, diarrhea, nausea and vomiting. Poisoning can also cause more serious symptoms like numbness, dizziness, and shortness of breath. Children and pets are at an increased risk of exposure due to their small size. 

Cube said health officials will continue investigating the death of the dog, which prompted the water tests at Hagg Lake. 

“There could be fecal contamination in the water that can lead to some of those similar things as well, so we take all of that seriously,” he said. 

Anyone who thinks they or their pets have become ill after swimming in a body of water in Oregon should email the Oregon Health Authority’s Cyanobacteria (Harmful Algae) Bloom Surveillance Program at HAB.Health@state.or.us.