South African President Cyril Ramaphosa on Thursday called the more than 70 deaths in an apartment block fire in Johannesburg "a great tragedy" and said he hoped an investigation would help prevent a repeat of the incident. Johannesburg remains one of the world's most unequal cities with widespread poverty, joblessness and a housing crisis. It has about 15,000 homeless people, according to the Gauteng government. The city suffers from chronic power shortages during which many resort to candles for light and wood fires for heat. The cause of the apartment block fire remains unknown.