Emergency services gathered in numbers on Yellowknife's School Draw Avenue said they were participating in a training exercise.
The exercise, at a lift station near Franklin Avenue, drew two fire trucks and three ambulances to the scene, and led several members of the public to report the apparent incident to Cabin Radio.
An official at the scene, next to the recycling centre near the intersection with Franklin Avenue, told reporters a training exercise was taking place.
Asked why the exercise involved so many emergency vehicles, each with lights and sirens, the official responded: "Well, go big or go home."
One fire truck left midway through the exercise to attend an apparent real call elsewhere downtown.
The training exercise involved a dummy placed into a confined space at the lift station, the official said.
The incident was initially reported by Cabin Radio and other outlets as an actual emergency, with no advance warning given.
This report has been updated to reflect that the incident was a drill.