U.S. journalist Peter Theo Curtis, who had been held hostage in Syria since 2012, was released to U.N. representatives Sunday, U.S. officials say.

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“We are all relieved and grateful knowing that Theo Curtis is coming home,” Secretary of State John Kerry said Sunday.

Curtis, a resident of Massachusetts and Vermont, is also an author fluent in Arabic and French, according to his family.

“My heart is full at the extraordinary, dedicated, incredible people … who have become my friends and have tirelessly helped us over these many months,” said Curtis’ mother, Nancy Curtis, of Cambridge, Mass. “Please know that we will be eternally grateful.”

She also said that her son, while working as a journalist in Yemen, became interested in the stories of “the many disaffected young men from the West coming to study Islam” and that wrote about them in his book, “Undercover Muslim,” published in the United Kingdom.

The Obama administration said Curtis is now safely outside of Syria but provided no details about the circumstances of his abduction or his release.

However, the Curtis family said the government of Qatar was involved in the released, which was executed on a humanitarian basis without ransom.

The family believes the 45-year-old Curtis was captured shortly after he crossed into Syria in October 2012

What prompted Curtis’ release also in unclear. However, the United Nations said it helped with the handover to U.N. peacekeepers in a village in the Israeli-annexed Golan Heights and that Curtis was released to American authorities after a medical checkup.

Curtis’ release comes after the militant group Islamic State recently beheaded American journalists James Foley, who abducted while covering that country's civil war.

Kerry said the United States over the past 24 months had reached out to more than 24 countries to help secure Curtis’ release “and the release of any Americans held hostage in Syria.”

A cousin of Curtis', Viva Hardigg, declined to provide details on the circumstances of his release, but confirmed that Curtis had been held by Jabhat Al-Nusrah, an al Qaeda affiliate in Syria.

  Curtis’ mother also said her was born Peter Theophilus Eaton Padnos in Atlanta, Ga. He graduated from Middlebury College, in Vermont, and has a doctorate degree in comparative literature from the University of Massachusetts.

Islamic State militants released a video last week of Foley’s beheading blaming his death on U.S. air strikes against their fighters in Iraq.

Foley's captors had demanded $132.5 million from his parents and political concessions from Washington.

A senior Obama administration official said last week the Islamic State had made a "range of requests" from the U.S. for Foley's release, including changes in American policy.

The Associated Press contributed to this report.