The first flight carrying migrants to Guantanamo Bay is en route and will arrive Tuesday evening, a U.S. Transportation Command official said.

The first U.S. military aircraft carrying detained migrants to Guantanamo Bay departed on Tuesday, U.S. officials said, as President Donald Trump's administration prepares to potentially house tens of thousands of migrants at the naval base in Cuba.

As tents went up in Guantanamo Bay, Cuba to hold migrants, attorneys at the Department of Homeland Security and Pentagon were still trying to determine whether it was legal to take the unprecedented step of flying migrants from the US southern border to the facility,