Pet owners, especially ones visiting over the holiday weekend, are being warned to keep their dogs out of the Russian River because of a toxin nicknamed "Very Fast Death Factor."

On Friday, Sonoma County officials posted signs along the Russian River warning of an algal bloom in the water that could be deadly if ingested. Although it is also toxic to humans, pets are more susceptible since they are more likely to swallow the water. "It is safe to walk through," Don McEnhill of Russian Riverkeepers told ABC 7. "There's algae at the edge of the river, you're not going to have to worry about walking through it, just don't suck your neighbor's toes after you do."

The warning comes after a 2-year old Golden Retriever named Posie died suddenly while on a August 29 rafting trip on the river. Toxicology reports later determined that she died from Anatoxin-a, which occurs naturally in blue-green algae. The neurotoxin acts so quickly it is also known as Very Fast Death Factor.

Blue-green algae appears naturally, but many believe the drought and rising temperatures are making it more prevalent since they prosper in warm, stagnant bodies of water. "This is a natural phenomenon made worse by global warming," Clayton Creager, watershed stewardship coordinator with the North Coast Regional Water Quality Control Board, told The Press Democrat. "As temperatures rise, we are going to see more blue-green algae. I guarantee you this is going to be a problem throughout the country."

Despite the recent death of Posie, officials aren't telling people to stay out of the water altogether. Tests did not detect the toxin in the water mid-stream. "We have not detected any danger in the water in the river or at big beach sites," said Dr. Karen Holbrook, Sonoma County's Deputy Public Health Officer. Officials recommend not drinking or cooking with the river water, keeping children and pets away from the algae, and to properly clean fish before eating.