WASHINGTON (AP) — Two Americans and the remains of a third held captive by Iranian-backed militants in Yemen were released on Wednesday in exchange for the return of about 250 of the Houthi rebels from Oman, according to the White House and sources in the region.

Oman’s state news said the American captives were flown out of Yemen on an Omani plane. It said 250 “Yemeni brothers” who received treatment in Oman have been returned to Yemen's capital, Sanaa, on two flights as part of the exchange.

“The United States welcomes the release today of U.S. citizens Sandra Loli and Mikael Gidada from Houthi custody in Yemen,” national security adviser Robert O'Brien said in a statement. “We send our condolences to the family of Bilal Fateen, whose remains will be repatriated as well.”

O'Brien did not mention the exchange, but thanked the leaders of Oman and Saudi Arabia for their help in securing the release of the Americans.

Kieran Ramsey, director of the administration's hostage recovery cell, said Loli and Gidada would soon be on their way back to the United States.

“Tragically, one of these Americans died during his unlawful captivity,” Ramsey said.

Kash Patel, a deputy assistant to Trump who worked on the deal, told The Wall Street Journal that Loli had been held by the Houthis for about three years and Gidada was held captive for about a year.

Yemen plunged into chaos and civil war when the Houthi rebels took over Sanaa in 2014 from the internationally recognized government. A Saudi-led coalition allied with the government has been fighting the Houthis since March 2015.

The war in Yemen has spawned the world’s worst humanitarian crisis, leaving millions suffering from food and medical shortages. It has killed more than 112,000 people, including fighters and civilians, according to a database project that tracks violence.

According to the newspaper, Saudi officials said they were reluctant to back the deal because it would allow dozens of Houthi militants trained on advanced drones and missiles to return to the battle zone.

Mohamed Abdel-Salam, a spokesman for the Iran-backed militants, also confirmed that about 240 rebels returned to Sanaa on two Omani flights. Among the returnees were wounded rebels who traveled to Muscat during peace talks in Sweden two years ago.

When contacted by The Associated Press, Abdel-Salam declined to comment on the release of the two Americans.

The release of the Americans came a day before a planned U.N.-brokered exchange of more than 1,000 prisoners between the Houthis and the internationally recognized government. The U.N. had said in September that the two warring sides agreed to exchange 1,081 conflict-related prisoners, including Saudi and Sudanese troops fighting on the side of the Saudi-led coalition.

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Associated Press writer Ahmed al-Haj in Sanaa, Yemen, contributed to this report.

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Corrects that release of Americans came a day before, not after, a planned U.N.-brokered prisoner exchange.