It was at first unknown what had caused the river to change colour so dramatically, but it soon emerged that it was the result of someone adding fluorescein to the water.
However, the culprits have still not been caught almost three weeks after the incident.
The colouring lasted several hours and no fish were harmed or coloured by the dye, which is commonly used as a tracer agent in water studies.
A study conducted at Environment Canada’s Pacific Environmental Science Centre in North Vancouver confirmed that the water was not toxic.
One hiker who saw the unusually-coloured water while walking by the river, Tyson Elder of Victoria, British Columbia, told The Sun: 'We had been hiking all day so to see something so bright and unexpected was kind of unnerving, especially because it is a popular tourist destination.