Officials from B.C.'s Ministry of Environment have determined that the substance used to turn the Goldstream River in Langford, B.C. neon green Thursday was non-toxic.
Lab results showed that the bright green hue was caused by a synthetic, organic compound called fluorescein, which is most commonly used as a fluorescent dye tracer in fluids.
Ministry staff say the substance is water soluble and don't think any fish or fish habitat were harmed by the incident.
Officials still don't know who dumped the fluorescein into the river.
Fire Chief Bob Beckett thinks the green waters may have been the result of an ill-conceived prank.
"In all likelihood it's a hoax. It may be a non-toxic substance but it's unfortunate that we had to utilize all sorts of resources to investigate this," he said.
