Five senators who visited the U.S. base at Guantánamo Bay, Cuba, criticized the migrant mission there over the weekend as a waste of resources, after the Pentagon estimated that the operation had cost $40 million in its first month.
The Senate delegation on Friday toured Immigration and Customs Enforcement facilities where about 85 migrants were being held, including in a prison that for years housed wartime detainees linked to Al Qaeda.
The senators also spoke with officials from the Defense and Homeland Security Departments. About 1,000 government employees, mostly from the military, are staffing the migrant operation.
The administration has sent fewer than 400 men, at least half of them Venezuelans, to the base since February as part of President Trump’s crackdown on illegal immigration. The authorities returned about half of them to facilities in the United States without explaining why scores of people needed to be housed at Guantánamo for short stays.
As of Sunday, there were 105 immigration detainees at the base.
Senator Jack Reed of Rhode Island, who was part of the delegation, faulted the administration on Sunday for “diverting troops from their primary missions” to Guantánamo.
Mr. Reed, the ranking Democrat on the Armed Services Committee, said in an interview that he was provided with an estimate that the operation had cost $40 million in the first month.
“All of that is extraordinarily expensive and unnecessary,” he said. Instead, the administration should “try to enhance ICE facilities in the United States.”
The others on the trip were Senators Jeanne Shaheen of New Hampshire, the top Democrat on the Foreign Relations Committee; Gary Peters of Michigan, the top Democrat on the Homeland Security Committee; Alex Padilla, Democrat of California; and Angus King, independent of Maine.
The Defense Department advised Congress that as of March 12, the Guantánamo migrant operation had cost $39.3 million, according to congressional aides, who spoke on the condition of anonymity because Pentagon and congressional communications are considered sensitive. That estimate covered a six-week period when the Trump administration had moved 290 migrants there, including 177 Venezuelans who were repatriated.
The daylong Senate trip on Friday was a low-profile event compared with ones by Defense Secretary Pete Hegseth and Kristi Noem, the homeland security secretary, who each brought news photographers with them. But just like during their visits, the senators were there when the administration flew in a small number of migrants: 13 Nicaraguans from an ICE facility in Louisiana. Tricia McLaughlin, a spokeswoman for the Department of Homeland Security, described them as “gang members.”
On Saturday, hours after the delegation issued a statement urging the administration to “immediately cease this misguided mission,” an Air Force C-130 cargo plane from San Antonio brought 12 more migrants to the operation.
It was the first military shuttle carrying migrants to Guantánamo since ICE began using less costly charter planes to transport migrants to and from the base on Feb. 28.
“After examining the migrant relocation activities at Guantánamo Bay, we are outraged by the scale and wastefulness of the Trump administration’s misuse of our military,” the five senators said in the statement.
They called the migrant operation “unsustainably expensive, operating under questionable legal authority, and harmful to our military readiness.”
Guantánamo is a particularly expensive place because it is cut off from the rest of the island by a Cuban minefield. The base produces its own energy and water, and supplies are shipped in from Florida by barge and aircraft.
The delegation was critical of the mission but not of the estimated 900 military members and 100 homeland security employees who had been mobilized to the base to carry it out.
Some troops “were rushed to Guantánamo Bay without notice, leaving their critical day-to-day military missions behind in order to build tents that should never be filled and guard immigrants who should never be held there,” the statement said.
“This would be better both economically and also in terms of legal clarity if the military were not involved,” it continued.
ICE decides when it needs military aircraft and the Pentagon provides them, according to two government officials who spoke on the condition of anonymity because they were not authorized to discuss the arrangements.
The congressional aides said the operation was governed by a secret memorandum of understanding between the Defense and Homeland Security Departments that says only migrants with ties to transnational criminal organizations be sent to Guantánamo Bay.
Mr. Hegseth said on Jan. 30 that Guantánamo would serve as a temporary transit point for “violent criminal illegals as they are deported out of the country.”
But the administration has declined to provide evidence that foreign nationals held at the base had violent criminal records. Checks of some whose identities have been made public showed their crimes amounted to illegally entering the United States, sometimes more than once.
The Department of Homeland Security has housed 395 migrants at Guantánamo Bay, some for just days, since the first 10 were brought there on Feb. 4, according to New York Times tracking of the transfers.
On Feb. 20, the United States sent 177 Venezuelans from Guantánamo to Honduras, where they were put on a Venezuelan plane and flown home.
All the others were returned to ICE facilities in the United States and in a few known instances were deported from there.
