The Washington Post confirmed Sunday morning that Washington Post correspondent Jason Rezaian has been released from imprisonment after being held in the country for 18 months.

Fred Ryan, the publisher of The Washington Post, issued a statement hailing the end of Rezaian's prolonged imprisonment, calling it a "545-day nightmare" for the correspondent and his family.

We are enormously grateful to all who played a role in securing his release. Our deep appreciation also goes to the many government leaders, journalists, human rights advocates and others around the world who have spoken out on Jason’s behalf and against the harsh confinement that was so wrongly imposed upon him.

After enduring such deplorable conditions and inhumane treatment, the top priority now must be Jason’s health and well-being.

Now a free man, Jason will be reunited with his family, including his brother Ali, his most effective and tireless advocate. We look forward to the joyous occasion of welcoming him back to the Washington Post newsroom.

Marty Baron, the executive editor of The Washington Post, reported that Rezaian, his wife Yeganeh Salehi and his mother had all exited the country.

News of Rezaian's freedom was first reported Saturday morning, but The Washington Post held off on declaring its Tehran bureau chief free until his plane left Iran this morning.

A niggling misunderstanding was to blame for the hours-long interval between the announcement of Rezaian's freedom and his exit from the country, The Washington Post reported Sunday. There was initially confusion as to whether Rezaian's mother, Mary, was on the flight manifest alongside her son. After that was resolved, a rule requiring the flight crew to be well-rested caused an additional delay.

Rezaian was arrested by Iranian authorities in the summer of 2014 and later sentenced after a secret trial on spying accusations derided as bogus by The Washington Post and other media observers. He has languished in prison since then, where his health took a turn for the worse.

Shortly after Rezaian left Iran, The Washington Post published a scathing editorial that called their correspondent "a political hostage" who was subject to the whims of a "sham trial" staged to gain leverage in the country's recent nuclear talks with the United States. The Post called for more stringent diplomatic relations with Iran, warning that U.S. interests could be in jeopardy.

The Post and Mr. Rezaian’s family will celebrate his safe return and that of the other Americans. But in the absence of a firmer U.S. policy, Iran’s attacks on Americans and vital U.S. interests will surely continue.

On Saturday, the United States confirmed Rezaian and three other Americans would be set free in a prisoner swap with Iran.