JOHANNESBURG, South Africa (AP) — An international aid group says South Africa has deported some 450 Zimbabweans who had fled instability and violence.

Medecins Sans Frontieres says one of its teams visited a detention center Friday, the day a presidential runoff was held in Zimbabwe. The aid workers found more than 450 men, women and children who said they had crossed the border in recent days.

When the aid team returned Saturday bringing supplies for the Zimbabweans, they found the center empty. Medecins Sans Frontieres says South African authorities confirmed that all the Zimbabweans in the center had been transported back across the border.