GUANTANAMO BAY, Cuba — The Trump administration has moved more than 30 people described as Venezuelan gang members to the U.S. Navy base at Guantanamo Bay, as U.S. forces and homeland security staff prepare a tent city for potentially thousands of migrants.

About a dozen of the men were brought in from El Paso, Texas, on Friday, as Kristi Noem, the secretary of homeland security, arrived at Guantanamo. She is the first senior member of the Trump administration to visit the migrant mission on the base in southeastern Cuba.

Noem was taken to the rooftop of the base’s aircraft hangar and observed as U.S. security forces led the deportees down the ramp of a C-130 military cargo plane to an awaiting minibus.

Maj. Gen. Philip J. Ryan, the army commander overseeing the migrant mission, stood beside her in combat uniform.

A Chinook transport chopper could be seen in the distance.

“Vicious gang members will no longer have safe haven in our country,” Noem said on social media, calling the men “criminal aliens.”

The White House has characterized this past week’s arrivals as members of Tren de Aragua, a Venezuelan gang that the United States has designated a “transnational criminal organization” for human trafficking and other crimes. A fourth group was inbound Saturday evening in what has become an emerging U.S. military air bridge from an immigration site in El Paso.

But the Trump administration has not released any of their identities, though they are believed to all be men, nor has it said how long they might be held at the island outpost.

The military has said agents of the Immigration and Customs Enforcement agency, or ICE, have been holding the first detainees.