The Justice Department’s top watchdog is considering whether to review the legality of any payments that the U.S. government may have made for the release of Army Sgt. Bowe Bergdahl and what role the FBI played in efforts to free the soldier from captivity in Pakistan, The Daily Beast has learned.

The department’s inspector general, Michael Horowitz, wrote a letter to a member of Congress this month saying that he had opened a “preliminary inquiry” into the matter, which concerns allegations that the U.S. government paid a ransom for Bergdahl’s freedom, and that in February 2014 the FBI sent a representative to the border region of Afghanistan and Pakistan expecting Bergdahl to be released.

Bergdahl didn’t show up and wasn’t freed until May of that year, when the Obama administration traded five Taliban prisoners held at Guantanamo Bay, Cuba, for the soldier, who had left his post in Afghanistan in 2009 and was captured.

The Daily Beast obtained a copy of Horowitz’s letter, which hasn’t been previously reported.

The inspector general’s inquiry, which has not yet led to a full investigation, marks the latest development in the still-unfolding story of Bergdahl’s capture, his time as a prisoner of the Taliban-aligned Haqqani Network, and what steps U.S. officials took to ultimately win his release.

Horowitz gave no indication when he would reach a final decision on whether to open a full investigation. He said that his office has been in touch with the FBI.

A spokesperson for the inspector general declined to comment, saying the office’s “practice is not to confirm or deny the existence of investigations.”

Horowitz is responding to allegations from Rep. Duncan Hunter, a vocal critic of the Obama administration's hostage release policy, who has been investigating the Bergdahl swap.

“Something obviously happened in early 2014, with the FBI in the lead, and the Department of Justice inspector general is best positioned to determine the facts and present them to Representative Hunter and the rest of Congress,” Hunter’s chief of staff, Joe Kasper, told The Daily Beast.

“There’s no hiding from the fact that on February 25, 2014, the FBI notified ISAF in Afghanistan that Bergdahl would be crossing the border,” Kasper said, referring to the International Security Assistance Force, which at the time was led by a U.S. general. “Now the question shifts to what led to that call and the expectation of the FBI that Bergdahl would be released. It wasn’t because Haqqani had a come to Jesus moment, that’s for certain.”

Hunter alleged last year to the inspector general the U.S. government had “paid [the] Haqqani Network for Bergdahl’s release and received nothing in return,” and he asked the watchdog to review the matter.

But the administration has never said it paid a ransom for Bergdahl. Instead, officials have argued that the prisoner swap was the only viable option. The administration faced opposition to the swap in Congress, after senior intelligence officials told lawmakers that the five Taliban were likely to return to hostilities against the U.S. if they were freed. And the families of some civilian hostages questioned why the president was willing to exchange prisoners for a soldier but not their loved ones.

President Obama and his top aides have said many times that the U.S. will not pay ransoms for hostages, despite the willingness of the Haqqani and other groups, including al Qaeda and ISIS, to barter for the lives of their captives.

That policy is at best a half-truth. In fact, the government has paid money to hostage-takers and helped hostages’ families do the same. That practice is likely to continue, according to kidnapping ransom experts and current and former U.S. officials.

Last year, The Wall Street Journal reported that the FBI helped facilitate a ransom payment to al Qaeda in 2012 from the family of Warren Weinstein, a kidnapped aid worker. The attempt to free Weinstein was unsuccessful and he was later killed in Pakistan by a U.S. drone strike.

Bergdahl is now facing a potential life sentence for leaving his post in Afghanistan. His case, which had already drawn significant national attention, is back in the spotlight as the subject of the second season of the acclaimed podcast “Serial.”