Updated

American freelance journalist Peter Theo Curtis, held hostage for nearly two years by the terror group Jabhat Al-Nusrah in Syria, has been released, the State Department said Sunday.

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

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 release, which was carried out 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 is 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 journalist James Foley, who was 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.”

"Just as we celebrate Theo’s freedom, we hold in our thoughts and prayers the Americans who remain in captivity in Syria," National Security Advisor Susan E. Rice said in a statement. "Notwithstanding today’s welcome news, the events of the past week shocked the conscience of the world. As President Obama said, we have and will continue to use all of the tools at our disposal to see that the remaining American hostages are freed."

White House Deputy Press Secretary Eric Schultz said: President Obama "shares in the joy and relief that we all feel now that Theo is out of Syria and safe. But we continue to hold in our thoughts and prayers the Americans who remain in captivity in Syria."

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

Curtis’ mother also said her son 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. airstrikes 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.