BEIRUT (AP) — U.S.-trained rebels who recently returned to Syria said Wednesday they have lost contact with one of their officers and that they are investigating reports that he defected and handed over his weapons to al-Qaida’s branch in the country.

The U.S. military said it had no indication that any U.S.-trained fighters have defected.

The allegations come only days after the group of about 70 rebels returned to Syria after training in Turkey as part of the U.S. program to train and equip rebels to take part in the fight against the Islamic State group.

Defection among the ranks of U.S.-trained rebels would be an embarrassment to the program, which has already been criticized as offering too little too late and failing to provide enough protection for those trained rebels once inside Syria. The selected rebels are said to undergo a thorough vetting process to ensure they focus on the fight against the IS.

U.S. officials have begun an overhaul of the efforts, including suggesting that the newly trained fighters operate as the New Syrian Forces, or NSF, alongside Syrian Kurds, Sunni Arab and other anti-Islamic State forces.

The U.S. Central Command confirmed Monday the graduates have re-entered Syria with their weapons and equipment and were to operate alongside existing western-allied forces.

In a new statement Wednesday, it said it had no indication that any New Syrian Forces fighters have defected to the al-Qaida branch in Syria, the Nusra Front, contrary to several press and social media reports. “Additionally, all Coalition-issued weapons and equipment are under the positive control of NSF fighters,” it said.

Navy Capt. Jeff Davis, a Pentagon spokesman, said any accounts of a defection are “patently false.” He said the U.S. is in contact with the latest group of trainees and as of Wednesday, all of them and their weapons were accounted for.

Another previous batch of rebels trained by the U.S. had previously been hit hard by the rival Nusra Front, also known as Jabhat al-Nusra. That group, made up of 54 fighters, was wiped out by the Nusra Front soon after it returned to Syria in July. Several members of the group were killed and others taken hostage while many fighters fled.

U.S. Central Command spokesman, Air Force Col. Patrick Ryder, said that those rebels largely disbanded — of the 54, one was killed; one is being held captive; nine are back in the fight; 11 are available but not in Syria; 14 returned to Syria but quit the U.S. program and 18 are unaccounted for.

The new allegations, pertaining to the second group of U.S.-trained rebels, were first circulated on social media after the group returned to Syria last week. The U.S.-based SITE intelligence group, which monitors militant websites, said supporters of the Nusra Front first reported that a group of those newly trained by America have handed over their weapons to the militants after they were arrested. The report made no mention of a defecting officer.

Other supporters of the Nusra Front posted pictures of what they said were weapons seized from the U.S. trained rebels.

In response to the allegations, the U.S. trained group, known as Division 30, posted a statement on its Facebook page saying it is investigating. If allegations are true, the group said, it will refer the officer in question to a military tribal on charges of treason because the weapons “belong to the Syrian people.” The group acknowledged losing contact with the officer but denied any contacts with al-Qaida’s affiliate.

Adding to the confusion, the officer, identified by Division 30 as Anas Ibrahim Abu Zayed, posted a statement on his Facebook page where he is identified as Anas Jalo, said he is no longer with Division 30 but works independently in the northern province of Aleppo. This suggested he was not working with al-Qaida’s affiliate, though he did not specifically say so.

Abu Zayed said he would not coordinate with the international coalition but continue to fight IS and the Syrian government forces on his own.

Earlier in the conflict, Abu Zayed was a member of another U.S.-backed rebel group known as Hazm, which was crushed late last year by the Nusra Front in a battle in Idlib province, in northern Syria.

The U.S.-trained rebels face significant challenges — from minuscule numbers in a war that has a myriad of competing armies, to social media postings that have described them as “dogs of America” and a media campaign that has tainted the group’s name even before they returned to Syria. Other rebels have derided them for agreeing to focus their fight on IS, away from Syrian President Bashar Assad, whom they consider the main target of their rebellion.

The head of the Britain-based Syrian Observatory for Human Rights, Rami Abdurrahman, said the U.S. trained rebels are so few and so ill-equipped that they have not shown to be relevant.

“So far, they have made no impact on the ground,” he said. “If they (Americans) want to train some, they must first train them on human rights issues and democracy before military training.”

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Associated Press writer Lolita C. Baldor in Washington contributed to this report.