Yemen's Shiite Houthi rebels have released six foreign hostages, including at least two Americans, and flown them to the Gulf country of Oman, which helped negotiate their release, officials said Sunday.

Houthi officials and officials at the airport in the rebel-held capital, Sanaa, speaking on condition of anonymity because they were not authorized to brief reporters, said three Americans, two Saudis and a British national detained earlier this year were released and flown to Oman.

The White House later confirmed that two Americans had been freed and sent to Oman, which it thanked for helping to secure their release. A statement from the National Security Council did not identify the Americans or detail the circumstances of their captivity or their release.

The White House said it had "worked tirelessly to secure the release" of the Americans since they were taken earlier this year.

"This outcome underscores that we have been and will continue to be tireless in pursuing the release of all Americans detained abroad unjustly, including those who remain in the region," the statement said.

A spokesman for a New Orleans-based logistics company, Transoceanic Development, confirmed that employee Scott Darden, 45, was freed. Darden was helping to deliver aid throughout the region for Transoceanic and relief organizations among its clients. It was not immediately clear who the other hostages were.

Yemen has been torn by a ferocious war pitting the Houthis and forces loyal to a former president against fighters loyal to exiled President Abed Rabbo Mansour Hadi, as well as southern separatists, local militias and Sunni extremists. The conflict escalated in March as a Saudi-led, U.S.-backed coalition launched airstrikes against the Houthis.

Officials from the Houthi media center refused to explain why they had detained the hostages, but said at least one of them is a journalist who "entered the country illegally" and "worked without notifying the authorities." The officials spoke on condition of anonymity because they were not authorized to release information to reporters.

A Houthi delegation left with the hostages to go to Oman, where they will resume talks with the U.N. envoy to Yemen, Ismail Ould Cheikh Ahmed, the Houthi officials said. The delegation is accompanied by another from the party of former President Ali Abdullah Saleh, who is allied with the Houthis, said Aref al-Zouka, the party's secretary-general.

Houthi spokesman Mohammed Abdel Salam held a press conference at the airport earlier Sunday. He refused to confirm the release of the hostages, saying only: "If we were to release anyone, it would be in exchange for the release of Houthis."

The British Foreign Office was unable to confirm the hostages' release. Omani officials could not be immediately reached for comment.

In June, American freelance journalist Casey Coombs, who was held by the rebels, was set free. Following Coombs' release, which Oman mediated, State Department spokeswoman Marie Harf said they were working to win the release of several Americans detained in Yemen.

Last month, the United Arab Emirates helped free British petroleum engineer Robert Douglas Semple, who had been held for 18 months after being kidnapped by al-Qaida in Yemen, which has expanded its reach in the country amid the fighting between Houthis and their opponents.

Transoceanic spokesman Ken Luce said Darden was held since March, had worked for the company for a little less than a year, and that his wife and son live in Dubai. Luce said he did not know if anything was given for the hostages' release.

"I am not privy to that information if there was anything," he said. "With the peace negotiations still ongoing, it's very difficult to ascertain anything."

The company's CEO, Gregory Rusovich, said in a statement, "We cannot begin to express the sense of joy and relief we feel with Scott's release. He has been safely evacuated and will be reunited with his family very soon."

Darden's wife, Diana Loesch, said she was leaving for Oman to be reunited with her husband. She said she had spoken to Darden over the phone and he said the Houthis had treated him well.

"He just landed in Muscat, actually. He just called me. He's both elated and overjoyed. I can't imagine what it must have been like for him to be in Sanaa for so long."

Darden also spoke with their 10-year-old son, Eesa. "He's very elated to finally be going to see his father after all these long months of not being able to talk to him or see him."