WASHINGTON (Reuters) - The U.S. State Department said on Tuesday that authorities were assessing the validity of a video released by Afghan militants that depicts U.S. hostage Caitlan Coleman and her Canadian husband, Joshua Boyle, who were seized four years ago.

State Department spokesman John Kirby said the United States was concerned about the welfare of the couple and their family and “continue to urge for their immediate release on humanitarian grounds.”

Coleman and Boyle vanished a few days after arriving in Afghanistan while on a backpacking trip near the Pakistani border in 2012. Coleman, who was pregnant at the time, has given birth to two boys while in captivity, ABC News reported earlier this year, citing her parents.

The Daily Beast online news organization said on Tuesday it had obtained the new video, which depicted Coleman saying her captors were threatening to kill the family if Taliban prisoners were executed in Afghan jails. Coleman pleaded for U.S. intervention, the newspaper said.

The Daily Beast said the Haqqani network, a Taliban affiliate operating in the Pakistan-Afghanistan border region, was holding the family captive and made the video and posted it online.

Kirby said the United States was “regularly engaged with the governments of both Afghanistan and Pakistan at the highest levels to emphasize our commitment to seeing our citizens return safely to their families.”