WILMINGTON, N.C. (CNN) — Two dog owners in North Carolina are devastated after their three dogs died within hours of exposure to blue-green algae.

Melissa Martin and Denise Mintz took the dogs to a pond in Wilmington to play and swim Thursday night.

When they were back home, one of the Westies started acting strangely, so they took her to an emergency animal hospital.

The other dogs started seizing and showing signs of liver failure.

All three died just after midnight Friday.

The owners want to warn other pet owners about the dangers of this toxic algae.

“People need to know about this. Like I said, if we had any clue this was ever a thing they would have never come. I had no idea,” said Martin. “And once we got to the emergency vet last night, they also weren’t sure.”

According to Blue Cross for Pets, blue-green algae blooms can produce harmful toxins that stop a dog’s liver from functioning.

Dogs can be exposed by drinking it directly or by licking their fur.

Exposure is often fatal.