Houthi rebels backed by Iran continue to hold Yemeni employees of the U.S. government hostage, the State Department confirmed Thursday. 

Earlier this week reports surfaced that showed 25 Yemenis in Yemen's largest city of Sana’a, who worked for the U.S. Embassy and USAID, had been arbitrarily detained by the rebel group. 

Young supporters of Yemen's Houthi movement raise their fists as they chant slogans during a demonstration in front of the closed U.S. Embassy in the capital of Sana’a Jan. 18, 2021, to reject outgoing US President Donald Trump's decision to designate the Houthi group a "foreign terrorist organization." (Photo by Mohammed Hamoud/Anadolu Agency via Getty Images)

THOUSANDS OF AMERICANS REMAIN STRANDED IN YEMEN AMID GROWING HUMANITARIAN CRISIS

A State Department spokesman told Fox News the "majority" of the hostages have been released, but that embassy staff "continue to be detained without explanation."

"We have been unceasing in our behind-the-scenes diplomatic efforts to secure their release," press secretary Ned Price told reporters Thursday. "We’ve seen some progress, and we’re continuing to work this critical issue."

The U.S. closed its Yemen embassy in 2015 amid a violent civil war that has since led to the greatest humanitarian crisis in the world, according to the United Nations.

Though while American diplomats were sent stateside, some Yemeni staff continued to work from home or as security guards at the embassy, Bloomberg reported.

Impoverished Yemen is mired in a devastating conflict between Iran-backed Houthi rebels and government forces backed by Saudi Arabia that has left tens of thousands dead and sparked a dire humanitarian crisis.  (Photo by Mohammed Hamoud/Anadolu Agency via Getty Images)

STATE DEPARTMENT REVOKES HOUTHIS' TERROR DESIGNATION DESPITE ATTACK ON SAUDI AIRPORT

It remains unclear which members of the embassy staff have been arrested by the rebel group, but the compound has also been breached, according to a State Department spokesperson.

"We call on the Houthis to immediately vacate it and return all seized property," the spokesman said. "The U.S. government will continue its diplomatic efforts to secure the release of our staff and the vacating of our compound, including through our international partners."

The U.S. has long called for an end to the conflict that has placed more than 20 million in "dire humanitarian need."

Supporters of Yemen's Houthi movement raise their fists as they chant slogans during a demonstration in front of the closed U.S. Embassy in the capital of Sana’a Jan. 18, 2021, to reject outgoing US President Donald Trump's decision to designate the Houthi group a "foreign terrorist organization." (Photo by Mohammed Hamoud/Anadolu Agency via Getty Images)

Saudi Arabia also joined the fight in 2015, following calls for military assistance from Yemen President Abdrabbuh Mansur Hadi after he was ousted by Houthi rebels.

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Saudi Arabia’s use of air raids has been condemned by human rights groups for contributing to the humanitarian crisis.

But calls for a ceasefire have been largely ignored by the Houthi rebels, who have made advances throughout Yemen over the last six years. 

Nick Kalman contributed reporting