Brussels fire service was called to Avenue Louise on Monday morning after reports of large plumes of smoke from the top of the Louise Tower.
Despite a large amount of smoke, the cause was a small fire caused by renovation works on the tower, according to spokesman Walter Derieuw.
The fire was started by work with a grinding wheel in a technical room under a ventilation grille, which led to the visible plumes of smoke. The workers on site had already started extinguishing the fire with fire extinguishers.
No casualties have been reported, and no evacuation procedure has been started.