Dog owners beware: there’s something in the St. John River that is deadly to dogs.

At least three have died after being in or near the river since Friday.

One was in the river near Hartts Island and two others went in at Carleton Park in Fredericton.

No one knows yet exactly what's in these waters that is so deadly to canines.

“Until we know exactly what happened, when we get the pathology report, we really don't know what happened,” said veterinarian Dr. Shawn Smith. “It seems really strange that there were three of them.”

There has been some speculation though.

“I was told it was an algae bloom, and if so, then that's just nature,” said dog owner Craig Vezina.

Lisa Deighan wonders if it is related to the spring floods.

“The water that was polluted during that time? All the sewage that was in the water? We're not sure, we don't know,” she said

Ever since this year’s flooding across the province, some dog owners have been wary of the river.

“We don't let him near that water,” Gladys Brennan said of her dog. “We keep him as far away as we can. There’s no way I’m letting my dog die because of contaminated water.”

Residents who bring their dogs to Carleton Park say there's no way to know there’s an issue with the water because there’s no signage anywhere.

“There needs to be signs,” Brennan said. “Not just for pet owners, but for kids too.”

Professionals say until the cause of death is known, it’s better to be safe than sorry.

“I would suggest that dog owners keep their pets out of the water in the St. John River, especially in that vicinity downstream,” said Smith.

Until those waters are deemed safe, pet owners are left with many unanswered questions.

Although the three dogs have been confirmed dead there’s still no confirmation on how they died, and we won't find that out until the results of the necropsies are released.

With files from CTV Atlantic’s Kate Walker.