A firefighter has fallen to his death while trying to extinguish a fire at the Gauteng Health Department in the Johannesburg CBD.Emergency services are on the scene trying to extinguish the blaze.An official says the fire started on the 23rd floor.“It’s a fire outbreak on the 23rd floor of the BOL building. The City of Johannesburg is attending to the fire. That’s all I can say at the moment.”Emergency workers have located four of the six firefighters who are trapped on the balcony of the top floor of the Health and Human Settlements building.A helicopter is being used to try and reach those still trapped.It’s not yet known how the fire broke out.Staff have been evacuated from the building, but two more firefighters are still trapped.Emergency services Nana Radebe says they're working to reach their colleagues.“We have a chopper on the scene and we’re trying to get them out but there are teams that have went inside as well to the search and rescue.”Glass has been falling from the 23rd floor onto the pavement down below where bystanders have gathered.