The first military flight carrying 10 “high-threat” migrants to Guantanamo Bay landed on Tuesday evening, according to the Defense Department. 

The C-17 plane, which took off from El Paso, Texas, landed at 7:20 p.m., U.S. Transportation Command said in a social media post.

The Pentagon later released a statement Wednesday saying that the “10 high-threat individuals are currently being housed in vacant detention facilities” at the high-security prison facility, which has been used to hold detainees linked to the 9/11 attacks.  

“This activity is in support of President Trump’s direction to the Secretary of Defense and the Secretary of Homeland Security to take all appropriate actions to expand the Migrant Operations Center at Naval Station Guantanamo Bay to provide additional detention space for high-priority criminal aliens unlawfully present in the United States,” the statement said.

In its own statement, the Department of Homeland Security said the 10 individuals are suspected members of the Venezuelan gang Tren de Aragua, and that the “worst of the worst criminals” will be held at Guantanamo.

The move stems from Trump’s executive order, signed Jan. 29, that directs the federal government to prepare the U.S. military installation in Cuba to house up to 30,000 migrants. 

While the Pentagon said the detention of the individuals was a “temporary measure” until they can be transported to their country of origin or another appropriate location, questions remain as to how long the migrants can legally be held there.

Observers have asked if Guantanamo Bay is able to house as many migrants as the Trump administration has touted. Only 779 men have been brought to Guantanamo since 2002, far below the tens of thousands of beds that the Defense Department has now been demanded to set up. And while the facility hosts a migrant-processing center, it has mostly been used for migrants brought via sea, not flown from the United States.

Still, Trump has touted his plan, claiming Tuesday that “there’s a lot of space to accommodate a lot of people.”

Top Defense and Homeland Security officials have also lauded the idea, with Defense Secretary Pete Hegseth declaring Monday that Guantanamo is “the perfect place to provide for migrants who are traveling out of our country.”

As of Monday, about 300 service members were at Naval Station Guantanamo Bay to support Trump’s plan, according to U.S. Southern Command, though several hundred more could soon arrive.