Afghan refugees take an educational class at Ft. McCoy U.S. Army base on September 30, 2021, in Ft. McCoy, Wisconsin. There are approximately 12,600 Afghan refugees being cared for at the base under Operation Allies Welcome. | Barbara Davidson/Getty Images

More than 700 Afghans have left the U.S. Army bases where they were temporarily housed to receive services for their transition to the United States, even before completing their resettlement, according to a report.

The number of "independent departures" could be higher than 700, Reuters reported Saturday, quoting two sources familiar with the data who also said the number includes more than 300 Afghans who walked out of Fort Bliss in Texas.

While it's not illegal for the Afghans who fled the Taliban on U.S. evacuation flights in August to leave the U.S. bases, their departure might cost other Afghan evacuees expedited work permits, apart from creating some other legal problems, a U.S. Citizenship and Immigration Services official was quoted as saying anonymously.

U.S. officials claim that the Afghans who left the military bases went through security screenings and likely have friends and relatives or resources to manage on their own.

About 2,600 Afghans have been resettled off base while 53,000 more are being housed on eight U.S. bases and another 14,000 are expected to arrive from Europe this week, according to Military News.

Reuters said it viewed a document called "Departee Information," which warns Afghans they would forfeit some advantages, including cash to help pay for travel to their destination in the U.S., and might not be able to return if they leave the base where they have been brought.

Last month, two Afghan men staying at the Fort McCoy U.S. Army base in Wisconsin were indicted by a federal grand jury on separate criminal charges of forcibly engaging in a sexual act with children and assaulting a spouse by strangling and suffocating her.

U.S. officials have also found that Afghan girls have been presented to authorities as the "wives" of much older men. Some girls have alleged they were raped and forced to marry older men who used them as a ruse to get on evacuation flights out of Afghanistan.

The State Department recently sought "urgent guidance" from other government agencies after child brides were brought to Fort McCoy.

Federal authorities are also investigating a recent assault on a female service member by three to four Afghan men at a Fort Bliss shelter complex, according to Gen. Glen VanHerck, head of U.S. Northern Command.

"In a population of 53,000, there have been eight reported cases of robbery and theft," which is below-average crime rates in the U.S., VanHerck responded, downplaying the incidents of reported criminal activity, Military News said.

"The investigation is currently with the FBI and have since provided acknowledgement that they received the case from Fort Bliss," Military Times quoted Lt. Col. Allie Payne, 1st Armored Division spokeswoman, as saying.

Among the thousands of Afghans who've arrived in the U.S., some 10,000 were flagged for additional security screening, and of those 100 were flagged for "possible ties to the Taliban or terror groups," sources with knowledge of the evacuation process previously told NBC News.

Two of those 100 were sent out of the country to Kosovo for an additional security review.

Republican Sens. Ted Cruz of Texas, Ron Johnson of Wisconsin, Tom Cotton of Arkansas and Kevin Cramer of North Dakota recently sent a letter to President Joe Biden, saying they were "deeply concerned that your withdrawal has imported an acute human rights crisis to our country."

Following the withdrawal of U.S. troops in Afghanistan, the Taliban quickly seized control of much of the country, eventually taking the capital Kabul in August and forcing the government to flee. In response to the unexpected speed at which they retook the nation, tens of thousands of Americans, Afghan allies, and others desperately left the country. It's been reported that as many as 100 U.S. green card holders are still waiting to be evacuated.

Last week, the Department of Homeland Security banned a charter flight carrying U.S. citizens evacuated from Afghanistan from landing in the U.S., The Hill reported.

Bryan Stern, the founder of Project Dynamo, which has been evacuating people from Afghanistan, told Reuters that a flight carrying 117 people, including 28 Americans and 83 green card holders, was denied entry into the U.S. after initially obtaining permission to land at the John F. Kennedy International Airport in New York City and Dulles International airport near Washington, D.C.

For its part, the Biden administration said all passengers had to be vetted before entering the U.S.

"All U.S.-bound flights must follow the established safety, security, and health protocols before they are cleared for departure," a DHS spokesperson said in a statement to Reuters. "This process requires flight manifests to be verified before departure to the U.S. to ensure all passengers are screened appropriately."

The U.S. withdrawal marked the end of the war in Afghanistan, which spanned nearly two decades.