Frustrated indigenous leaders and human rights advocates called out Justin Trudeau on Thursday after the prime minister described mercury contamination at Grassy Narrows First Nation as "very much" an Ontario issue.

The Northern Ontario First Nation has dealt with mercury poisoning since a paper mill in Dryden, Ont., dumped 9,000 kilograms of the substance into nearby river systems in the 1960s.

A group of youth from a remote First Nations community where mercury has poisoned the river for nearly 50 years travelled 1,700 kilometres to the Ontario legislature Thursday to demand action from government.