WASHINGTON (AP) — U.S. authorities have removed immigrants from detention facilities at the Guantanamo Bay naval base as a federal court in Washington weighs a challenge by civil rights advocates to holding immigrants at the offshore military station.

A spokesperson for the U.S. Southern Command on Thursday said that no “illegal aliens” are being held at Guantanamo Bay in Cuba after 40 immigrants were flown off the base on Tuesday to Louisiana.

Officials declined to specify why the immigrants were transferred to the U.S. or to share their names and nationalities.

Additionally, two U.S. officials said on condition of anonymity, to provide additional details on the movement, that while the 40 immigrants have been removed, it doesn’t mean that the facility won’t be used in the future — it’s just not decided yet.

Future “high-threat” detainees may be sent there, the officials said.

President Donald Trump has said he will send the worst criminal migrants to Guantanamo Bay, but civil rights attorneys say many detainees transferred there don’t have a criminal record and that the administration has exceeded its authority in violation of U.S. immigration law.

Civil rights attorneys sued the Trump administration this month to prevent it from transferring 10 migrants detained in the U.S. to Guantanamo Bay and filed statements from men held there who said they were mistreated in conditions that one of them called “a living hell.”

The transfer of detained immigrants to Guantanamo Bay “constitutes an unlawful removal” and violates the Immigration and Nationality Act, advocacy groups including the ACLU said Thursday in a court filing.

The Trump administration says it commands broad authority to hold immigrants with final deportation orders at Guantanamo Bay.

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Lee reported from Santa Fe, New Mexico.