Lammertsen says while they believe most of the material has been collected, it’s not a certainty.

“The problem is, is that material could be anywhere in the storm system between the source and the river, and we are containing it at the river, and it just takes time.

“Because the substance is sitting on the surface of the river, it’s easy to contain,” she adds. “We are using a vac truck to remove the substance from the surface of the water.”

It’s not clear if this was an accidental spill or deliberate. Crews are now going through the catchment area for the storm drain outfall.

She says because the oily substance was released away from the city’s water treatment plant, drinking water has not been affected.

“This catchment area is mostly the industrial area, so it is downstream of the water system.”

Alberta Environment is also investigating. It’s not clear if any wildlife has been or could be affected.

The City is reminding people not to dump or release any cooking oils or grease, industrial waste, chemicals like pesticides and herbicides, trash, soil, leaves, grass, sawdust, cement or concrete waste, solvents or pains, gas or motor oil, antifreeze or transmission fluid or any soaps or detergents.

According to the City’s website, there is a Drainage Bylaw with fines ranging from $75 to $10,000, however a spokesperson tells LNN it’s not certain whether that bylaw would or could apply in this instance, because the investigation is ongoing.

Lethbridge News Now has also contacted Alberta Environment to find out whether it is also investigating the source of the substance, and whether there could be any fines or other potential consequences associated with the release of the oil.