Alberta Environment is investigating after a gas flare-up at a Petro-Canada refinery led to a plume of yellow and black smoke being leaked into the Edmonton sky.
Officials from the province tell CTV News unknown quantities of unburned hydrocarbons were expelled from a boiler stack around 7 p.m. Wednesday.
The Petro-Canada boiler reportedly was experiencing a water supply issue, Alberta Environment said, creating a loss of steam in the boiler which led to discharge of the unusual smoke.
Officials from the province were on scene Wednesday night shortly after the incident and they set up three downwind monitoring stations.
Testing revealed no elevated levels of air contaminants such as hydrocarbons or sulphur.
Alberta Environment officials said there is no evidence of any impact to the environment.
More investigations are underway to find up why the water supply issue happened.