WASHINGTON — The first U.S. military flight to deport migrants from the United States to Guantanamo Bay has departed and is expected to land Tuesday evening, two U.S. officials said. It is the first step in an expected surge in the number of migrants sent to the Navy base in Cuba, which for decades was primarily used to detain foreigners associated with the Sept. 11, 2001, attacks.

President Trump has eyed the facility as a holding center and said it has the capacity to hold as many as 30,000.

Defense Secretary Pete Hegseth, who was assigned to Guantanamo Bay when he was on active duty, has called it a “perfect place” to house migrants. Additional U.S. troops have arrived at the facility in the past few days to help prepare.

Amy Fischer, director of the Refugee and Migrant Rights Program at Amnesty International USA, decried the use of Guantanamo to house migrants.

“Sending immigrants to Guantanamo is a profoundly cruel, costly move. It will cut people off from lawyers, family and support systems, throwing them into a black hole so the U.S. government can continue to violate their human rights out of sight. Shut Gitmo down now and forever!” Fischer said in a statement.

There are approximately 300 service members supporting the holding operations at Guantanamo Bay, and the numbers will fluctuate based on the requirements of the Department of Homeland Security, which is the lead federal agency. At least 230 of those service members are U.S. Marines from the 6th Marine Regiment, who began deploying Friday.

In addition, the U.S. flew Indian migrants back to India on Monday, and that flight was still in progress as of midday Tuesday, one of the officials said. The officials spoke on the condition of anonymity to provide details not yet made public. There are more than 725,000 immigrants from India living in the U.S. without authorization, the third-most of any country after Mexico and El Salvador, according to the Pew Research Center.

Copp and Baldor write for the Associated Press. AP writer Rebecca Santana contributed to this report.