The new director of the military’s Defense Intelligence Agency on Tuesday left open the possibility that at least one of the Taliban officials exchanged for U.S. soldier Bowe Bergdahl last May could return to the battlefield.

Marine Lt. Gen. Vincent Stewart, who took over as the chief of DIA in January, acknowledged the possibility during a House Armed Services Committee hearing on worldwide threats. Stewart said that over the last five years, about 18 percent of all detainees who have been released from the prison at Guantanamo Bay, Cuba, have “gone back into business” as insurgents and that another 11 percent are suspected of having done so.

“So if those numbers translate, of the five who were transferred, probably one in five could be expected to go back into the business,” Stewart said.

Stewart appeared to be addressing a hypothetical possibility based on recidivism rates among detainees released from Guantanamo. But his remarks could fuel the politically charged debate over the release of the Taliban figures from the military prison.

Bergdahl, 28, was recovered by U.S. Special Forces on May 31, 2014, in a swap for the five. Now a sergeant, he is believed to have left his platoon’s outpost in Paktika province, Afghanistan, on June 30, 2009, after growing disillusioned with the U.S. military’s campaign there. He was captured afterward by enemy forced and held captive in Pakistan by the Haqqani network, an insurgent group allied with the Taliban, until a deal brokered through the government of Qatar was reached last year.

The detainees remain under observation in Qatar, but are expected to be freed this spring under the agreement. CNN reported last week that one of the “Taliban 5” is suspected of already having reached out to the Taliban associates in Afghanistan. Qatari Foreign Minister Khaled al-Attiya, in Washington on Monday, denied any of the five had attempted to re-engage in militant activity, Reuters reported. The detainees are “living according to the agreement we signed with the United States.”

The trade for Bergdahl has proved controversial. Soldiers in his unit have said they believed he deserted them, a felony crime in the military. A new investigation was launched into his disappearance in June, but the Pentagon has disputed that any decision on how to handle the case has been reached.

The nonpartisan Government Accountability Office determined last summer that the White House violated federal law in swapping Bergdahl for the Taliban officials without giving Congress 30 days notice. The Pentagon has disagreed with that assertion, saying the Justice Department the swap was legal beforehand and that the United States had a small window of time in which to free Bergdahl.