Alberta Environment this week released a 27-page preliminary report of the incident at Obed Mountain mine, outlining activities to date, water quality testing results and other associated factors.
It issued an environmental protection order to mine owner Sherritt International and Coal Valley Resources to rectify the issue.
The spill, which contained clay, mud, shale and coal particles, entered the Apetowun and Plante creeks, which feed the much larger Athabasca River.
Several toxic compounds were also included, including mercury, arsenic, lead, cadmium and manganese.
Alberta Environment spokeswoman Jessica Potter said the companies had been working with officials to remediate the spill.
“We have asked community water treatment plants to continue to refrain from using the river as a resource when the plume is going through," she told Reuters.
Additionally, Potter said the operators’ order served as a formalisation of the clean-up and also provided deadlines for the companies to complete the work.
She told the news service no decision had been made yet as to whether the agency would issue environmental charges to Sherritt and Coal Valley.
According to Canadian media, high levels of pollutants have been found as far as 40km downstream of the spill.
The Canadian Press said it was approximately 180km from Fort McMurray but had been dissipating.
“We began our testing the morning after this happened and, to date, these samples have indicated that the sediment travelling downstream in the Athabasca River poses no risk to human health or safety," Sherritt coal senior vice president Sean McCaughan told the news agency.