Nearly four dozen Afghan troops training in the U.S. have vanished in less than two years, officials confirmed Thursday.

At least 44 Afghan troops have left their assigned bases since January 2015, calling into question their training programs' screening processes. Of those 44, 25 were reported Absent Without Leave, or AWOL, in 2015, and 19 have gone AWOL this year.

At a press briefing Thursday, Pentagon spokesman Peter Cook said 32 of the missing Afghans had been located.

One of the eight Afghan students who disappeared in September of this year turned up at the Canadian border, the Pentagon reported. Police caught the student. FoxNews.com has reported that many Afghans who go AWOL from training in the U.S. have made their way through a pipeline running from Texas to Toronto.

A U.S. defense official, speaking on condition of anonymity, told Reuters that the frequency of Afghan troops disappearing from military training was truly concerning and “out of the ordinary.”

The Defense Dept. “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,” Pentagon spokesman Adam Stump told Fox News.

The network helping Afghans move along the pipeline from the U.S. to Canada includes the students' relatives, women living in the U.S. illegally who transport the Afghans to bus stations or airports, and an Iranian taxi driver who shuttles them across the Canadian border, FoxNews.com has learned.

When foreign troops who leave military training in the U.S. are gone for more than 24 hours, officials alert Homeland Security, according to the Pentagon.

Afghans who train at U.S. military bases are vetted to make sure they don’t have a sketchy background or ties to militant groups in the Middle East, Stump added. The defense official told Reuters there was no evidence that those who vanished posed any threat to the U.S.

The military training program, on which the White House has spent billions of dollars since 2002, brings in troops from around the world to train at U.S. bases.

Fox News' Lucas Tomlinson contributed to this report.

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