Canadian authorities have suffered a frustrating blow in their search for two teenage fugitives wanted for the highway killing spree across remote northern Canada that left Australian tourist Lucas Fowler, his US girlfriend and a botanist dead.

The Royal Canadian Mounted Police announced on Monday a possible sighting of Kam McLeod, 19, and Bryer Schmegelsky, 18, at a garbage dump could not be substantiated after a "thorough and exhaustive