Apache said more than 250,000 gallons of so-called produced water were released from its Zama production area in Alberta. The company said the fluid was mostly saltwater though it contained trace amounts of oil from extraction operations.
The company published an update to its response, saying it still was not sure what caused the incident.
"While our priority right now is remediation and restoration, we are investigating the cause and will develop a solution to prevent a similar incident," the company said last weekend.
Apache said it has a long history of environmental stewardship when responding to releases. Produced water did not reach the Zama River in Alberta province, though aboriginal communities said forested areas near the spill were heavily damaged. The company said vegetation studies were under way.
The company said there were no injuries associated with the release. It is working with provincial and federal regulators on site to deal with the release.