At least 44 members of the Afghan National Defense and Security Forces (ANDSF), which includes police and military units, have gone missing since January 2015. They disappeared while participating in U.S.-based training programs, including eight since last month alone, Reuters has learned from the Pentagon.

“The Defense Department is assessing ways to strengthen eligibility criteria for training in ways that will reduce the likelihood of an individual Afghan willingly absconding from training in the U.S. and going AWOL (absent without leave),” Adam Stump, a Pentagon spokesman who revealed how many ANDSF troops have gone missing, told Reuters.

Although other foreign troops have disappeared while training in the United States, an unnamed U.S. defense official told Reuters the frequency of ANDSF members running away was concerning and “out of the ordinary.”

According to the official, “there was no evidence any of those who had absconded had carried out crimes or posed a threat to the United States.”

In January 2015, an Afghan soldier was granted asylum and allowed to remain in the United States despite having absconded and apprehended trying to sneak into Canada.

Afghan troops have gone missing on U.S. soil “presumably in an effort to live and work illegally in America,” notes Reuters, citing the Pentagon.

The Afghan service member who was granted asylum was one of five ANDSF officers — two policemen and three soldiers — who went missing in September 2014 while participating in separate U.S.-based training programs.

Eventually, the two policemen were found right outside of Washington D.C., and the military officers were apprehended while trying to sneak across the Canadian border.

Reuters reports:

The military training program brings troops to the United States from around the world in order to build on military relations and improve capabilities for joint operations.

In some cases, officials said, the Afghan students who went missing were in the United States for elite Army Ranger School and intelligence-gathering training. The officials did not identify the missing troops or their rank.

Local and federal authorities, particularly the U.S. Department of Homeland Security (DHS), have been involved in efforts to locate the missing Afghans after they are reported missing.

“Even though the troops were in the United States for military training, they were not necessarily always on a military base,” reports Reuters.

“If students under the military program are absent from training for more than 24 hours, they are considered to be ‘absent without leave’ (AWOL) and the Department of Homeland Security is notified,” it adds.

The Pentagon spokesman explained that “Afghans in the U.S. training program are vetted to ensure they have not participated in human rights abuses and are not affiliated with militant groups before being allowed into the United States.”

Taliban jihadists and other terrorists have occasionally infiltrated the Afghan army. Some of the infiltrators have carried out attacks on Afghan and U.S. forces.

However, such insider attacks, officially known green on blue attacks, “have become less frequent due to tougher security measures,” notes Reuters.

The news outlet adds:

Although the number of disappearances is relatively small — some 2,200 Afghan troops have received military training in the United States since 2007 — the incidents raise questions about security and screening procedures for the programs.

They are also potentially embarrassing for U.S. President Barack Obama’s administration, which has spent billions of dollars training Afghan troops as Washington seeks to extricate itself from the costly, 15-year-old war. The disclosure could fuel criticism by supporters of Republican presidential nominee Donald Trump, who has accused the Obama administration of failing to properly vet immigrants from Muslim-majority countries and has pledged a much tougher stance if he wins.

Since the Afghanistan war started in October 2001, the U.S. has invested nearly $70 billion on training and developing the ANDSF.

Nevertheless, the Afghan troops continue to face capability gaps. The Taliban currently controls more territory than at any time since it was dethroned in 2001.

Tens of thousands of Afghans have been admitted into the U.S. legally in the wake of the ongoing 15-year-old war in their country.

More than 31,000 Afghans have resettled in the United States as refugees, asylees, or special immigrant visa recipients since President Barack Obama escalated the conflict soon after taking office in 2009.

According to a Breitbart News tally gleaned from federal data released under the Freedom of Information Act (FOIA), at least four Afghans have been apprehended trying to sneak into the United States across the U.S.-Mexico border.

“Experts said low morale and insufficient training to fight the Taliban could explain the troops leaving, in addition to a dearth of economic opportunities in the impoverished country,” reports Reuters.