Two Committee to Protect Journalists staffers have been released from detention in Tanzania and have left the country, the organization announced Thursday.

Angela Quintal and Muthoki Mumo were permitted to return to their hotel in Dar es Salaam after being taken to an unknown location and subjected to "several hours of questioning," according to a news release. Their passports were also returned.

"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. "It is deeply ironic that through their unjustified and abusive detention of our colleagues, Tanzanian authorities have made their work that much easier. 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."

Simon commended the attention brought to the case by "journalists, media and press freedom organizations, and government officials," and noted that the South African and Kenyan governments were of particular assistance.

Quintal, the Africa program coordinator at the Committee to Protect Journalists, and Mumo, the organization's sub-Saharan Africa representative, were in Tanzania for a reporting mission. They were detained on Wednesday by "officers who identified themselves as working with the Tanzanian immigration authority," according to the organization. The officials took their passports, phones and computers.

Quintal sent a message Wednesday from her verified Twitter account saying she and her colleague were "being taken for interrogation by Tanzanian authorities and we don't know why?"

According to the Committee to Protect Journalists, "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 of their Twitter accounts remained suspended at the time of publication.

The US State Department was "closely following" the case, a spokesperson told CNN Wednesday.

"We continue to engage with our Government of Tanzania counterparts on a wide range of issues, including those related to human rights," the State Department said in a statement. "The United States remains committed to the values of democracy, rule of law, freedom of expression, and prosperity in Tanzania."