More than 35 firefighters were called to a tower block in Wood Farm, Oxford, after an alarm went off.
The six fire engines, two special appliances and two ambulances surrounded Foresters Tower shortly after noon on Saturday.
The crews sealed off the entrance to the tower as firefighters went in search of the fourth-floor fire and reports of smoke.
But at 1.45pm nothing had been found.
Incident manager Matt Dangerfield said: “There was a smell of smoke and the alarm went off on level four. Nothing was found and we believe it was an alarm system failure. This number of vehicles is standard for any incident in a high rise block.”