WINNIPEG - People in the northern Manitoba village of Sherridon are looking for answers after acidic, orange-coloured water was seen flowing from a mine clean-up site into Kississing Lake.

Work has been ongoing since last year to clean up seven million tons of mining tailings that are leaching sulphuric acid into the water. Nearly 60 years ago, Sherritt Gordon shut down its copper and zinc mine after 20 years of operation, but its environmental footprint is still being cleaned up.

Crews have been using lyme to neutralize the tailings and the water in the surrounding Camp Lake. Once treated, the water flows into a polishing pond where the contaminates are supposed to settle safely at the bottom before the clean water then flows out into nearby Kississing Lake.

But Debbie Hatch, a community council member in Sherridon, said she noticed in late November that something wasn't right.

"Usually the water coming over that weir is clear, but this time it was a dark 'orangey' colour," she said. "It was very upsetting."

Eric Reder, Manitoba campaign director for The Wilderness Committee, said he believes that flow continued for two days.

"In terms of immediate effects, I'm pretty sure it's going to kill any aquatic life it touches," he said. "You can't put a fish in a jar of vinegar."

A spokesman for Mining Minister Dave Chomiak said a water treatment plant malfunctioned and discharged acidic water into the polishing pond.

"There was some water that was discharged from the polishing pond into Kississing Lake that did not meet water discharge standards," the spokesman said. "The incident has been reported to Environment Canada."

The spokesman added that remedial action was taken, including stopping the discharge and readjusting the plant accordingly, as well as employing a stop log at the outflow site to allow the contaminated water more time to sit in the polishing pond.

A spokesman from the company in charge of the clean-up did not return a call Thursday.