U.S. immigration authorities have cut the frequency of deportation flights to Haiti to one per day this week, the result of a sharp decline in the number of Haitian migrants trying to enter the United States, according to three administration officials.

U.S. Immigration and Customs Enforcement operated as many as seven flights per day to Haiti last week, returning more than 700 migrants daily. On Tuesday, the agency returned 57.

The cause of the drop-off is that most of the Haitians taken into custody last month at a makeshift camp in Del Rio, Tex., have been processed by immigration authorities, and far fewer Haitians have crossed since the camp’s closure on Sept. 24, according to the three officials, who spoke on the condition of anonymity because they were not authorized to discuss the data with reporters.

President Biden’s handling of Haitians at the border drew scathing criticism from Democrats and Republicans, and some of the president’s opponents claimed that his administration had released most of the migrants into the United States.

The latest Department of Homeland Security statistics show the opposite: Most of the roughly 15,000 who reached the Del Rio camp were returned to Haiti or opted to cross back into Mexico to avoid being sent to their destitute homeland.

“As the number of Haitian migrants being encountered has decreased, so has the number of flights,” said Eduardo Maia Silva, a DHS spokesman.

“As we implement the [Center for Disease Control and Prevention’s] public health authority, DHS continues to conduct regular expulsion and removal flights to Haiti and a number of other countries in our hemisphere,” he said, referring to Title 42 of the U.S. public health code, which allows authorities to bypass normal immigration proceedings and deny migrants an opportunity to remain in the United States to seek asylum.

The Biden administration has used Title 42 to “expel” more than 7,000 migrants to Haiti since Sept. 19, according to the latest information from the United Nations.

U.N. officials, rights groups and many leading Democrats have called on the Biden administration to halt the expulsions, saying Haiti is too unstable to accept the sudden return of thousands of its citizens.

One of Biden’s top political appointees at the State Department, attorney Harold Koh, denounced the administration’s use of Title 42 as “inhumane” and “illegal” while submitting his resignation. Biden’s special envoy to Haiti, Daniel Foote, also quit over the Haiti flights.

In May, the Biden administration deemed Haiti to be too unsafe to accept deportations, a decision that preceded the assassination of the country’s president in July and a 7.2-magnitude earthquake in August that devastated the country’s southern peninsula. DHS officials say they changed their determination and initiated the expulsion flights after thousands of Haitians waded across the Rio Grande to the Del Rio camp.

ICE has sent 68 flights from Texas to Haiti since then, records show. The frequency of the flights peaked last week at six or seven per day, split between Port-au-Prince, the capital, and Cap-Haïtien, the country’s second-largest city.

“We have never seen such a massive number of removal flights to a single country in this short period since we began reporting in January 2020,” said Tom Cartwright, whose advocacy group, Witness at the Border, tracks ICE operations using publicly available data.

The 57 expulsion flights to Haiti that the Biden administration operated during the most intense period of activity between Sept. 19 and 30 accounted for more than half of all ICE flights during that period, according to Cartwright.

Haitian family groups have accounted for more than 40 percent of those returned by the Biden administration, U.N. data show. Migrants traveling as part of a family group were about two-thirds of those who arrived in Del Rio, according to DHS.

The latest data shows Haitian families have been expelled at a much higher rate over the past several weeks than family groups from other countries. Many of the Haitians were living in Brazil, Chile and other South American nations before embarking on the journey to the U.S.-Mexico border.

The Biden administration has said Haitian migrants were mistaken or duped into thinking they would be allowed to enter the United States, but U.S. immigration enforcement data shows a far greater percentage of Haitians were allowed to remain in the United States to pursue asylum claims before the Del Rio surge.

In January, about 55 percent of Haitian border-crossers were expelled to their country under Title 42, but that figure fell to 8 percent in July.

Anthony Faiola in Miami contributed to this report.