The Department of worldwide relations and cooperation says South African journalist Angela Quintal and a colleague returned to their hotel in Dar es Salaam, Tanzania, in the early hours of this morning.
"Sanef also welcomes the speedy probe into the matter by the Department of International Relations (Dirco) and calls on Dirco to exert pressure on their Tanzanian counterparts".
South Africa's High Commissioner Thami Mseleku is meeting with the pair to discuss the details of their arrest.
However, on Thursday morning, Ndhivo Mabaya, spokesman for South Africa's foreign ministry, told AFP that "they were both released".
The Mail & Guardian said that according to Mabaya, there are a number of issues that the South African High Commissioner will want to be addressed by Tanzanian authorities.
Quintal tweeted before 1am on Tuesday morning that she and her colleague had been released.
The Twitter accounts of two have been suspended, leading to confusion whether Ms Mumo and the former Mail & Guardian editor Quintal have been released.
Dirco confirm safety of journalists in TanzaniaAngela Quintal: What happened? We don't know why.
Ms Muthoki Mumo, a former Nation reporter, and her CPJ colleague Ms Angela Quintal were detained on Wednesday in their hotel room in Dar es Salaam and then taken to an undisclosed location by people who identified themselves as immigration officials. "We call on the authorities to immediately release them and return their passports", he added.
"We need to understand the circumstances". The officials searched the pair's belongings and would not return their passports when asked.
They were detained by Tanzanian authorities on Wednesday night for reasons that remain unclear.