Officials in Lethbridge say an unknown substance that was released into the Oldman River on Thursday poses no risk to the public and the waterway is now safe for recreational users.

The city says a limited amount of the substance appeared to have entered the river from a storm water outflow on the east river bank north of Highway 3.

Officials put out a warning to the public to stay off the river in that area until crews could figure out exactly what the substance was and where it came from.

On Friday, it was determined that stagnant storm pond water entered the river but that it was not dangerous to the public.