(CNN)A small number of ISIS detainees have "recently" escaped from detention by US-backed Syrian Democratic Forces, according to a US official with direct knowledge of the program. The official described the incident as involving "less than five ISIS fighters."
ISIS fighters escape from US-backed detention in Syria
The fact that escape is possible has underscored the security worries: There have been urgent and growing concerns inside the US military and intelligence community about the security arrangements for hundreds of foreign ISIS fighters being held by the Syrian Democratic Forces, according to several US and coalition officials.
The fate of these fighters has taken on urgency because of the sheer number of ISIS operatives being held. US officials have said there are thousands of fighters in Syrian Democratic Forces hands, the majority of them Syrian nationals. Of the detained fighters, some 500 are foreigners from 40 countries, according to one of the officials.
As more fighters are captured and the detainee population swells, officials worry that the camps are becoming new ground for ISIS to regroup and develop new networks. The official with direct knowledge pointed out that in the days of large US-held detention facilities in Iraq, such as Camp Bucca, the US failed to realize quickly enough that such networks would take shape inside detainee populations.
ISIS leader Abu Bakr al-Baghdadi was held at Camp Bucca in 2004, and in retrospect many experts believe the beginning of ISIS could be traced to those days.
"We don't want to make the same mistakes," the official said. The official also confirmed that US personnel are conducting some interrogations under strict military procedures in order not to not violate any laws. Their interrogations have resulted in valuable intelligence, the official said: Two of the fighters were associates of the ISIS killer known as Jihadi John, responsible for the brutal beheadings of several hostages, including Americans. The two men have provided intelligence on the possible location of the remains of some of the dead Americans.
The Pentagon and State Department are trying to encourage the transfer of detained foreign fighters to their home countries. But some countries appear to be resisting this on potential legal grounds, the official said. Nations of origin would be in the position of taking custody from the Syrian Democratic Forces, which is not a legally recognized power or nation. The Syrian government, which is in legal control of the country, obviously is not involved in any detention efforts.
Defense Secretary James Mattis, during a recent trip to Europe, failed to secure any transfer agreements.
"I wanted to bring this problem to everyone's attention, under no illusions about that we would solve everything in 24 hours," Mattis told reporters while traveling.
The Pentagon is openly acknowledging the security problem.
"These aren't necessarily the best detention facilities in the sense of they are being held in Syria and not in the most secure area. I think it would be better if we make sure they are prosecuted, if possible, in their countries of origin," said Katie Wheelbarger, principal deputy assistant secretary of defense for international security affairs.
"There were certain days where we are seeing 40-50 a day were being captured, so a capacity problem is very real," she said.