A fire sent dark smoke billowing from the European Commission headquarters in Brussels, forcing hundreds of workers and visitors to evacuate.

The smoke was seen rising Monday afternoon from the floor where the EU commissioners have their offices.

At least a half-dozen fire trucks quickly moved into the Commission compound and a helicopter swooped overhead as smoke continued rising over an hour after the fire was detected.

The firefighters were checking every floor of the building, but it was unclear where the fire had started.