A former employee of the paper mill in Dryden, Ont., has written a letter describing what he says is a hidden dump of dozens of mercury barrels that could be the source of on-going health concerns downstream at Grassy Narrows First Nation.

Mercury contamination from Reed Paper's chemical plant in Dryden during the 1960s and 70s is a well-studied environmental disaster.

But a recent government-funded report by environmental scientists revealed there is an on-going, yet unknown, source of mercury in the water where people at Grassy Narrows continue to catch and eat fish, their staple food.

"I am writing this letter out of guilt and possibly to share some info you might not be aware of," Kas Glowacki writes in an email sent last summer and obtained this week by CBC News.

Glowacki says in the letter that he worked at the mill in 1972 as a labourer and as part of his job he filled more than 50 barrels with a mixture of mercury and salt and then drop them in a pit.

Drums of mercury 'dropped' in a pit

"I was amazed at the amount of mercury that was pooling around my shovel as I dumped it into the drums," he writes, later saying, "The drums were dropped, not placed, into the pit."

He describes the pit as being lined with plastic and "up on the hill above the river."

Glowacki's letter prompted a flurry of correspondence between Grassy Narrows and Ontario's Ministry of Environment and Climate Change.

The chief wrote to Minister Glen Murray saying his community, where people continue to suffer mercury poisoning, was surprised by Glowacki's letter and unaware of the dump site.

An ministry official wrote back to say the Ministry has known about it all along.

"A mercury disposal site was established on a hillside west of the mill in 1971," wrote the senior environmental officer in Kenora. "Since its establishment the groundwater around the site has been sampled twice yearly with analysis for mercury...This site is not a source of mercury contamination."

But the chief of Grassy Narrows First Nation doesn't believe the Ministry has even located the dump that Glowacki wrote about and says mercury levels in the river that flows into his community haven't been monitored by the government since the 1980s.

"I am shocked and dismayed by Ontario's failure to protect our people who live downstream from this reported toxic mercury dump," Chief Simon Fobister Sr said in a news release on Monday.