A warning for anyone planning to spend time at the Guadalupe River near Canyon Lake this weekend: The U.S. Army Corps of Engineers says that the water south of the Canyon Lake Dam could be hazardous to your health.

A warning sign is up asking people to not swim or let animals drink water at the river after a dog died and two others became ill last weekend.

Kinsey Perry and her friend Larissa Parker took their dogs to the river last Saturday.

"Within about 30 minutes I noticed my friend Larissa’s dog Meiko was making a choking and hacking noise," Perry recalled.

They checked Meiko’s throat but couldn’t find anything.

“It was within seconds, I turned around and saw Hunnie flailing in and out of the water, convulsing," Parker described.

“I turn around and Hunnie was convulsing, she was seizing and she was just completely disoriented, so we ran over there and, when I went to grab her, she was completely limp," Perry said.

After attempting CPR on Hunnie, they drove for help.

“I drove as fast as I could to the vet clinic and the whole way I kept feeling her heart and I could tell her heartbeat was slowing fading and about two miles away from the vet clinic, two exits away, I felt it stop, her heart stopped," Perry said.

Hunnie died. Meiko and Perry’s other dog were fading fast.

"My dog Hallie couldn’t even use her back limbs, she was completely disoriented. [Larissa’s] dog Meiko was displaying the same symptoms. It was awful," Perry said.

The dogs got help in time and should recover.

The Guadalupe Blanco River Authority (GBRA) is testing the water to determine what was in it.

The veterinarian believes that the dogs were poisoned by blue green algae that may have bloomed in the water.

“It’s not as likely to have a bloom in water that is moving such as what we have down here in the Guadalupe River. But because the veterinarian thought the symptoms of the dog were consistent with blue green algae poisoning, we have to consider that and alert people to that possibility," said Marcus Schimank, the Canyon Lake manager for the U.S. Army Corp of Engineers.

Perry and Parker say that the area needs to be closed until the toxin is identified.

“I can assure, I’ll never take my dogs to the river or lake again after this situation," Parker said.

"If it killed my 40-pound dog within a matter of 20 to 30 minutes, if a child were in that river, I can’t imagine what a parent would be feeling like right now," Perry said.

The GBRA expects results from the water test any day now. Until then, they’re asking people to avoid areas of rivers or creeks where the water is stagnant.