WASHINGTON, March 13, 2025 (BSS/AFP) - The United States has flown all 40 migrants being held at its Guantanamo military base in Cuba to the state of Louisiana, a US defense official said Wednesday.

Washington began flying migrants to the notorious base -- best known as a detention facility for suspected militants captured during the "War on Terror" -- early last month as part of President Donald Trump's immigration crackdown.

"I can confirm that all 40 were flown back to Louisiana" on Tuesday, the defense official said, referring questions about why they were moved to the Department of Homeland Security, which did not immediately respond to a request for comment.

The Trump administration has launched what it billed as a major effort to combat illegal migration that has included immigration raids, arrests and deportations, including via Guantanamo.

The president unveiled a surprise plan in January to hold up to 30,000 migrants at the base, but a far smaller number of detainees -- more than 200 in total -- have passed through the facility at some point so far.

The Guantanamo prison was opened in the wake of the 9/11 attacks and has been used to indefinitely hold detainees seized during the wars and other operations that followed.

Conditions there have prompted an outcry from rights groups, and UN experts have previously condemned it as a site of "unparalleled notoriety."

The base still holds 15 people incarcerated for militant activity or terrorism-related offenses, among them several accused plotters of the 9/11 attacks, including self-proclaimed mastermind Khalid Sheikh Mohammed.