WASHINGTON (AP) — The Trump administration spent at least $40 million to deport roughly 300 migrants to countries other than their own as immigration officials expanded the practice over the last year to carry out President Donald Trump’s goals of quickly removing immigrants from the U.S., according to a report compiled by the Democratic staff of the Senate Foreign Relations Committee.

The Democrats on the Foreign Relations panel, led by Sen. Jeanne Shaheen, criticize the practice of third country deportations as “costly, wasteful and poorly monitored” in the report and call for “serious scrutiny of a policy that now operates largely in the dark.”

The State Department, which oversees the negotiations to implement the programs, has stood behind the practice of third country deportations and defended it as a part of Trump’s campaign to end illegal immigration.

“We’ve arrested people that are members of gangs and we’ve deported them. We don’t want gang members in our country,” Secretary of State Marco Rubio responded when asked about some of the third country deportations at a Senate hearing last month.

The report states that El Salvador, Rwanda, and other nations received lump-sum payments ranging between $4.7 million and $7.5 million for accepting deportees, yet many migrants ended up returning to their original countries after U.S. payment of additional flights.

This practice has drawn concerns from immigration advocacy groups who believe it violates due process and exposes deportees to countries notorious for human rights abuses. Shaheen emphasized that this approach wastes resources, highlighting that alternatives could have avoided unnecessary costs.

Overall, the effectiveness and accountability of the Trump administration’s method of deporting migrants to third nations continue to be contested.