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. Researchers have reported that more than 90 per cent of the people in Grassy Narrows and the Wabaseemoong (White Dog) First Nation show signs of mercury poisoning.

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.

Ministry of the Environment officials did geophysical testing, but found no barrels.

The group Earthroots sent volunteers to take soil samples of the site near the Wabigoon River and say their testing found high levels of mercury. The government says that testing took place in a different area than the worker originally pointed them to, so officials will review the new information and take “appropriate investigative action.”

Gord Miller, the Earthroots board chair and former environmental commissioner of Ontario, said the results provide “a solid reason to believe” there is a deposit of mercury below the surface.

“We can’t prove that this material is actually leaching into that drainage system, (but) something is leaching into the draining system because it’s in the fish,” he said.

“Something has to be done. There is more than enough evidence to justify a complete geotechnical survey of the site to find and establish if there are further hotspots, any more deep concentrations of mercury.”

NDP critic Peter Tabuns said such ongoing contamination would never have been allowed to happen in the Greater Toronto Area, so it shouldn’t be happening in Dryden. New testing should be done quickly, he said.

“My assumption is technically it’s not difficult at all,” Tabuns said. “Apparently a group of volunteers with plastic bags were able to go to the site area that was identified and get the sample that implicates this site in ongoing mercury contamination, so I don’t think that’s difficult. The question is: are they willing to do it? It’s not a question of the ability to do it.”

Premier Kathleen Wynne has said she is committed to cleaning up mercury in the river, but doesn’t want to take any steps that could stir up more of the element trapped in the sediment on the bottom of the waterways.

The government earmarked $300,000 for Grassy Narrows to work with John Rudd, the lead author of a study on the local mercury poisoning, and another $300,000 for government scientists to start to implement Rudd’s suggested work plan to deal with the problem.