Immigration lawyers told the Associated Press they know of more than 40 individuals who have been abruptly discharged or whose status has become questionable. Government spokespeople said they were unable to explain the discharges due to ongoing litigation.

Some were not given a reason for the sudden discharge, while others were told their family members abroad makes them a security risk, or the Defense Department was not able to complete the required background checks, the AP reports.

More than 5,000 immigrants were recruited into the military in 2016, and roughly 10,000 are currently serving throughout all branches of the military. To be eligible for military service, immigrants need some sort of legal status, like a student visa.

Lucas Calixto is a Brazilian immigrant who was recently discharged from the U.S. Army. He filed a lawsuit against the military branch, hoping to be able to return to service.

“It was my dream to serve in the military,” Calixto told AP. “Since this country has been so good to me, I thought it was the least I could do to give back to my adopted country and serve in the United States military.”

Those who were discharged had all signed enlistment contracts and taken the Army oath. Some were already undergoing training and receiving pay, while others were in a “delayed entry” program. All expected to become naturalized citizens after receiving an honorable service designation, which one can get after a few days at boot camp, but none were able to get that far, according to the report. Now, their legal status is at risk. Some fear returning to their home country, knowing they could face danger as a previous U.S. military service member.

According to the Defense Department, “All service members (i.e. contracted recruits, active duty, Guard and Reserve) and those with an honorable discharge are protected from deportation.” These immigrant reservists and recruits, however, were an “uncharacterized discharge,” neither honorable nor dishonorable.

Immigrants have been serving in the U.S. military since the country’s founding, but recent programs have encouraged the enlistment of those with medical specialization or certain language fluency. In 2002, President George W. Bush signed an executive order for “expedited naturalization” of immigrant soldiers, aiming to boost enlistment numbers. Years later, this became the Military Accessions Vital to the National Interest (MAVNI) program, an official recruiting process.

Since 9/11, nearly 110,000 immigrants have gained citizenship through military service, the Defense Department reports, some winning honors for exemplary service.

MAVNI was scrutinized when President Obama allowed DACA recipients — individuals brought to the country illegally as children — to be eligible for enlistment. Additional security clearances were added before recruits could go to boot camp. President Trump added even more barriers shortly after taking office, MAVNI was suspended, and hundreds of recruits had their contracts canceled.