A Boston woman believes toxic blue-green algae poisoning may have claimed the life of her family’s 16-year-old dog after a swim at a local park.

Elivia Savadier Sagov said both of her dogs became sick after swimming in the Charles River Friday at Millennium Park in West Roxbury, Massachusetts. She told CBS Boston that the water appeared clean, but she noticed her dog, Dobby, drinking from it before she could stop her.

“It was so beautiful and clear. I saw her drink some water, which I didn’t like, but I didn’t catch her soon enough,” Savadier Sagov said.

Both dogs showed signs of illness within hours of being exposed to the water, according to Savadier Sagov. While both became sick, Dobby, a 16-year-old, experienced more severe symptoms, including muscle stiffness, seizures, weakness and gastrointestinal issues, Savadier Sagov claimed.

Dobby died Sunday, her owner said, leaving her with the belief that the blue-green algae poisoning may have been responsible.

“This year I was very aware [of the algae]. I thought maybe not to let them in the water at all, but it’s so tempting,” Savadier Sagov told CBS Boston. “We miss her terribly. It’s just been so sudden. Just really miss her.”

The Charles River Watershed Association told The Independent it is unaware of any recent water testing in the section of the Charles River near Millennium Park where the dogs reportedly swam. However, the river has experienced cyanobacteria, or blue-green algae blooms, nearly every summer over the past decade, with the longest lasting 12 weeks in 2020, according to the organization’s website.

Cyanobacteria can produce toxins that are dangerous to people and animals, with dogs especially at risk because they may drink contaminated water or ingest algae while swimming in rivers, lakes and ponds, according to the Cornell University College of Veterinary Medicine.

Toxic blooms are most common in warm, stagnant, nutrient-rich water, and the toxins can linger for weeks even after the algae is no longer visible.

The toxins can attack the nervous system, liver or skin, causing vomiting, diarrhea, weakness, muscle tremors, seizures, collapse, difficulty breathing, and, in severe cases, death.

Symptoms can appear within minutes to hours, and because there is no antidote, owners should seek immediate veterinary care if exposure is suspected, according to Cornell.

Savadier Sagov thinks these warning signs need to be posted at local spots.

“I almost feel there should be permanent notices here that state it very strongly: July and August, there is likely to be algae,” she told CBS Boston. “If there’s rain, you may not even see the scum, but spores are still in the water. And once the dog gets this, the vets say there’s nothing that can be done.”

Following the incident, officials indeed issued a precautionary cyanobacteria advisory for a stretch of the Charles River, including Millennium Park and Cutler Park, with warning signs posted at access points, CRWA River Science Extern Marielena Lima told The Independent Tuesday.

The Massachusetts Department of Public Health will also collect samples from the river Wednesday to test for cyanobacteria cells and two types of cyanotoxins known to impact the liver: microcystins and cylindrospermopsin, Lima added.