Up to 30 other men are believed to have already escaped from the property before the police made their raid.
According to the police, the group was held captive without access to either clothes or documents. Three men, also Ethiopians, have been arrested on suspicion of human trafficking.
South Africa, Africa's most industrialized country, attracts millions of migrants every year. Many of them are from other African countries and a large number lack permission to stay in the country.
Last year, over 80 Ethiopians were found locked up under "inhuman conditions" in a house in the same Johannesburg suburb, writes AFP.
