In an apparent setback for the Obama administration’s campaign against Islamic State extremists, Al Qaida’s branch in Syria has captured a commander of a new U.S.-trained anti-jihadist force and several fighters, according to Turkish officials and Syrian rebels.

The abduction, confirmed on the ground but with details disputed by the Pentagon, underlines the risk the United States incurs by fielding a force in a battlefield so messy that a group trained to target one set of jihadists is seized by a rival set of jihadists before it even really began fighting enemy No. 1, the Islamic State.

Accounts of the incident from Turkish officials, Syrian rebels, Turkish media and a posting on the commander’s Facebook page, offer this sequence of events:

On Wednesday, Nadim Hassan, head of the 30^th Division rebel faction, and several of his men were meeting in the vicinity of Azaz, near the Turkish border. Nusra gunmen arrived in pickup trucks and detained Hassan and his companions; it is unclear how many of other men seized also were involved in the U.S. government’s $500 million “train-and-equip” effort. Some accounts said the men were taken during lunch; others claim it was on the road after the meeting.

“The total number of kidnapped is 23 and about 18 are from the T&E group,” said Yusuf Salih, a Turkmen commander of the Sultan Murad Brigade rebel faction. His figures couldn’t be independently verified. “Five are from the 30^th, but not from the T&E program. They were in consultation with each other in Azaz.”

In interviews with local and international media before his abduction, Hassan had confirmed his involvement in the program, which has been widely criticized as too small and too slow to effectively combat the Islamic State.

Hassan’s 30^th Division was set up to absorb graduates of the U.S. training effort, though it’s been delayed because of a lengthy vetting process and the reluctance of Syrian rebels to sign up to fight the extremists when their main goal is toppling the Assad regime in Damascus.

Shortly before his capture, Hassan had complained in an interview with The New York Times that the Pentagon had failed to provide night-vision goggles, had yet to announce an anti-Assad component to the fight and hadn’t made a clear pledge to the rebels to provide U.S. air support should they come under attack by the regime. He also told the newspaper that some fighters had threatened to quit over unpaid expenses.

A Turkish official, speaking on condition of anonymity because of the sensitivity of the matter, described Hassan as a key logistical commander of the American-led training program, a position that potentially complicates efforts to negotiate his release.

While the Nusra Front shares two common enemies – the Islamic State and Syrian leader Bashar Assad – with the more mainstream rebel factions, the group falls under the umbrella of al Qaida, which opposes American involvement in the region. U.S. warplanes periodically attack the Nusra Front, including a strike on July 28 on what the Pentagon described as “a tactical unit,” driving speculation that the timing of the group’s capture of a U.S.-linked commander the next day was no coincidence.

Two U.S. intelligence officials speaking on condition of anonymity to discuss classified information, admitted that as many at two top officials of the train-and-equip program had been detained by Nusra Front but cautioned that not all of the other captives were part of the American program.

The Obama administration’s formal responses to the matter have been vague, with conflicting information from various agencies. The Pentagon, for example, on Wednesday issued a forceful denial that any rebel involved in the U.S. effort had been captured, with spokesman Navy Capt. Jeff Davis telling McClatchy that the trainees “are all present and accounted for.”

In a later exchange Thursday, however, Davis modified his answer, expressing concern about the reports but saying the Pentagon would neither confirm nor deny the mass abduction because “we’re not the spokesmen for every group in Syria, friendly or otherwise.”

“I hope I’m giving you enough of a steer here,” Davis said. “I’m telling you I’m not disagreeing with the reports. If you want to report based on what you’ve seen, I don’t think you’re going to see the Department of Defense pushing back.”

At the State Department, spokesman Mark Toner said he wouldn’t use the word “setback” to describe the specific incident but acknowledged that “the train-and-equip program has been slow to get off the ground.” During the daily news briefing, Toner condemned the reported abduction and addressed reporters’ frustration with the inability of the U.S. government to explain what happened.

“Quite frankly, it’s Syria,” Toner said. “We don’t have eyes on the ground there.”