Joburg EMS firefighters are conducting damping-down after a fire broke out early this morning at the corner of Bree and Harrison Streets in Johannesburg's CBD. EMS says a large transformer located on the ground floor is suspected to be the cause. No injuries have been reported.  EMS says the exact cause will be confirmed following a full investigation once all emergency operations have been completeted.Joburg EMS spokesperson Xolile Khumalo explains.