WASHINGTON—Homeland Security Secretary Kristi Noem is slated to make a trip Friday to Guantanamo Bay, as the Trump administration steps up use of the naval base in seeking to emphasize toughness against migrants it says have criminal backgrounds.

Guantanamo Bay, a U.S. base in Cuba since 1898, may soon house thousands of detained migrants, following a proposal by the Trump administration.

The American Civil Liberties Union on Friday demanded access to migrants flown by the U.S. military to Guantanamo Bay, Cuba, saying the Trump administration has provided virtually no information about the migrants and that the detentions raise questions about violations of U.