TORONTO -- An environmental group believes it may have found a source of ongoing mercury contamination that has plagued a northern Ontario First Nation for more than 50 years.

The Grassy Narrows community, near the Manitoba border, has dealt with mercury poisoning since a paper mill in Dryden, Ont., dumped 9,000 kilograms of the substance into the Wabigoon and English River systems during the 1960s.

But mercury concentrations haven't decreased in 30 years and dangerous levels are still present in sediment and fish, causing ongoing devastating health and economic impacts in the community.

A former worker at the Dryden mill came forward last year saying he had buried more than 50 barrels of mercury and salt in a pit in 1972.

The group Earthroots sent volunteers to take soil samples of the site near the Wabigoon River and say testing found high levels of mercury.

Ministry of the Environment officials did geophysical testing last year of the area the worker pointed them to, but say he has now pointed Earthroots to a different location, and that they will review the new information "and take appropriate investigative action."