Environment Canada is investigating Vale SA's smelting operations in Sudbury, Ont., for allegedly leaking toxic run-off into local waterways since at least 1963.
The allegations are contained in a warrant the government agency used to seize documents, computers and related materials from Vale's Sudbury offices on Oct. 8 as part of its investigation into potential violations of the Fisheries Act.
In the warrant, Environment Canada accuses the company of allowing "acutely lethal" seepage from the smelter waste piles into water frequented by fish, and of knowing about the leakage since at least 1997.
The warrant contains allegations not proven in court.
The investigation was triggered after a Sudbury resident noticed a "foamy, lime-green coloured substance in a creek" in October 2012.
The document says Environment Canada officers followed the seepage back to Vale's Copper Cliff slag storage area.
