"Environment Canada’s Enforcement Branch has an ongoing investigation into this incident to determine if a contravention of federal environmental legislation has occurred, and continues to work in cooperation with provincial regulatory authorities," said department spokesman Mark Johnson.
Alberta is also looking into whether charges will be laid under provincial legislation.
Both governments declined to comment further while the investigation is under way.
On Tuesday, Alberta's energy regulator released a report that found Plains Midstream was to blame for the leak, which released about 460,000 litres of oil into the Red Deer River. The pipe, which crossed the river, cracked wide open during a flood that saw stream flows about 10 times normal.
The regulator found the company failed to meet government inspection standards. It also ignored warnings from consultants hired to assess the situation and its own internal experts, who told Plains there was a problem four years before the line broke.
Plains Midstream also failed to heed provincial heavy streamflow advisories.
The oil tainted a long stretch of the river and flowed into Gleniffer Lake, a reservoir used for boating, fishing and swimming.
Drinking water had to be trucked in for residents of 750 permanent and recreational homes at the lake. The marina was closed. Rafting, fishing and guiding businesses were affected.
Governments have two years after the incident to lay charges, putting the deadline at June 7.
Last year, Environment Canada fined 13 companies for violations of the Fisheries Act or the Canadian Environmental Protection Act.