The maintenance activity, originally scheduled for April, comes amid media reports that thousands had taken to the streets and shut shops in Thootukudi to protest against the expansion of the smelter.
Under new measures unveiled by Prime Minister Justin Trudeau's office on Tuesday, the Canada Border Services Agency will gain new powers to stop companies that try to dodge duties.
The accident killed 19 people, left hundreds homeless and unemployed and caused sludge to wash downstream into the neighbouring state of Espírito Santo.
Gungnir's drill campaign would begin in the second quarter of 2018 with 20 diamond drill holes testing six target areas over a strike length of more than 8 km.
Kinross Gold to pay $950,000 to settle civil charges that it failed to ensure its payments in Africa were not being used to bribe government officials.