Kenyan journalist Muthoki Mumo and South African journalist Angela Quintal—both staff members of the Committee to Protect Journalists (CPJ)—have been released after being detained in Tanzania with their passports seized, Reutersreports.

The women were detained on Wednesday night after Tanzanian authorities entered their hotel room and confiscated their passports. After being transferred to an unknown location and interrogated about their work, they were then released in the early hours of Thursday morning. The reason of their detainment was initially unclear.

Mumo and Quintal were on a fact-finding assignment with the CPJ, according to the organization.

"During their detention, Quintal and Mumo's phones and computers were also seized," the CPJ says in a statement. "While they were detained, a false tweet saying they had been released was sent from Quintal's personal Twitter account and repeated attempts were made to access Quintal's email."

Both Quintal and Mumo's Twitter accounts have been and remain to be suspended.

Ali Mtanda, spokesperson for the Tanzanian Immigration Department, states that Mumo and Quintal were arrested for "violating the terms of their visas by holding meetings with local journalists."

"They were supposed to get a separate permit for that," he adds.

Joel Simon, executive director of the CPJ, explains further that the pair traveled to Tanzania to learn about the challenges facing the Tanzanian press and to inform the global public.

"It is deeply ironic that through their unjustified and abusive detention of our colleagues, Tanzanian authorities have made their work that much easier," Simon continues. "It is now abundantly clear to anyone who followed the latest developments that Tanzanian journalists work in a climate of fear of intimidation. We call on the government of Tanzania to allow journalists to work freely and to allow those who defend their rights to access the country without interference."

Quintal is the CPJ's Africa program coordinator and Mumo is the organization's sub-Saharan Africa representative.

Though Mtanda states that both women journalists were free to stay in Tanzania as long as they obeyed the terms of their 90-day visas, the CPJ says they have left the country.