South Africa's Department of International Relations and Cooperation (Dirco) said the two journalists are back in their hotel.
"Angela Quintal and Muthoki Mumo traveled to Tanzania to understand the challenges facing the Tanzanian press and to inform the global public", Committee to Protect Journalists executive director Joel Simon said in a statement.
Tanzanian Authorities took their passports upon arrest, and are yet to return them.
He added that both women were now at the South African embassy in Tanzania's economic capital Dar-es-Salaam.
Ms Quintal is the CPJ's Africa program coordinator while Ms Mumo is the organisation's sub-Saharan Africa representative.
Giving details on their arrest‚ Gallens said: "After approximately five hours‚ Quintal and Mumo were then returned to their Dar es Salaam hotel at around 3am - but without their passports". The officials searched the pair's belongings and would not return their passports when asked. For now, Quintal and Mumo are well and will stay at their hotel, Mabaya said.
A South African news site, News24, reported that a tweet had been sent from Ms Quintal's account before it was suspended appearing to allay fears by confirming that she and Ms Mumo had been released but her family claimed that someone else may have been in possession of her phone. "This shows someone is using her account".
Rights groups and media advocates have expressed concerns about the freedom of expression in the country. "The United States remains committed to the values of democracy, rule of law, freedom of expression, and prosperity in Tanzania".
This after appealing for help on social media, saying they had been taken for interrogation by the Tanzanian authorities.
"If they want to engage themselves in anything more than a normal visit then they have to request appropriate permits", spokesperson for Tanzania's immigration ministry Ally Mtanda is quoted to have said.