The Richardson Building in downtown Winnipeg was cleared out on Wednesday evening based on reports of possible smoke near the top floor, but it turned out to be steam from a boiler equipment test.
Fire crews converged upon the office tower on Portage Avenue and Main Street just before 6 p.m.
Among those who had to get out of was Adam Abraham, who was working on the 20th floor when the alarms went off.
"I couldn't hear or smell anything. We heard a lot of sirens, obviously, coming this way from the fire trucks, but nothing unusual," he said.
In an email to CBC News, a building official said steam was being released from the boiler "as part of an annual pressure test on the equipment."