The number of Haitian migrants attempting to cross into the United States fell by more than 90 percent in October after the Biden administration aggressively ramped up its use of deportation flights, according to preliminary U.S. Customs and Border Protection data obtained by The Washington Post.

CBP figures show about 1,000 Haitians were taken into custody along the Mexico border last month, down from 17,638 in September, when huge crowds waded across the Rio Grande to a makeshift camp in Del Rio, Tex., creating a humanitarian and political crisis for the Biden administration.

Biden officials responded to the Del Rio surge by using the Title 42 emergency public health order to “expel” more than 8,500 migrants back to Haiti, sending as many as seven flights per day from Texas to the destitute Caribbean nation.

The mass expulsions were denounced by immigrant advocacy groups and members of the president’s own party, who noted that Haitian families — including thousands of women and children — were being returned at higher rates than migrants from other nations. Many had fled Haiti years earlier and had been living in Chile, Brazil and other South American nations. They opted to leave for the United States after hearing from relatives and others that jobs were available and Haitians would be allowed to enter.

After U.S. authorities launched the return flights, roughly half of the Haitians who arrived to the Del Rio camp in September chose to cross back into Mexico, according to the Department of Homeland Security.

Tens of thousands more Haitians who want to cross the border have opted to wait in Mexico for now, or temporarily seek asylum there, fearful they will be returned to their home country if they attempt to enter the United States illegally, according to U.S. authorities and United Nations migration officials.

“The Biden administration has pivoted to a clear, definite position on how it’ll be treating arrival of Haitian migrants,” said Cris Ramon, an immigration policy analyst in Washington. “By leaning heavily on expulsions, it’s making people think twice.”

Most of the Haitian migrants do not have strong asylum claims because they resettled in other countries after Haiti’s devastating 2010 earthquake. In interviews about why they want to come to the United States, they cite deteriorating economic conditions and racial discrimination in South America, as well as the belief the Biden administration would let them stay.

In May, the Biden administration expanded temporary protected status for Haitians living in the United States without legal status, saying that deportations to their country would be too unsafe. Haiti’s woes deepened after the country’s president was assassinated in July and a devastating earthquake struck in August.

The Biden administration began allowing more and more Haitian border crossers to remain in the United States and apply for asylum; the percentage of Haitians expelled under Title 42 fell from 55 percent in January to 8 percent in July, CBP data show.

Then 15,000 Haitians showed up in Del Rio. The Biden administration was caught unprepared and left embarrassed by scenes of Border Patrol agents on horseback charging at families along the riverbanks.

The White House turned sharply toward expulsions. The president’s top advisers viewed the deportation flights as an unpalatable but necessary measure to assert control at the border and discourage tens of thousands of other migrants from crossing.

Thousands of Haitians are now adrift in Mexico, sleeping in packed shelters and flooding the country’s overwhelmed asylum agency with applications. Mexican authorities have also started deportation flights directly to Haiti.

More than 26,000 Haitians have requested asylum in Mexico in 2021, up from fewer than 6,000 in 2020 and 2019, Mexican government data show.

“Some of these people may not need asylum but other migration alternatives to be in Mexico, so they aren’t overwhelming the asylum system, which should be helping people who need international protection,” said Sibylla Brodzinsky, a spokeswoman for the U.N. Refugee Agency office in Mexico City.

U.S. Immigration and Customs Enforcement has sent 80 flights to Haiti since Sept. 19, more than any other nation during that time, according to Witness at the Border, an advocacy group that tracks deportations.

When the Biden administration announced the increase in Haiti flights in September, authorities said they would work with Brazil, Chile and other nations where the migrants started their journeys, asking those governments to allow the Haitians to return. But the Biden administration has not announced any agreements or flights to those countries.

The decline in Haitian migrants eased some pressure on the Biden administration at the border in October. About 160,000 border crossers were taken into CBP custody during the month, preliminary figures show, down from 192,000 in September. It was the third consecutive month that border arrests have declined, after peaking at 213,593 in July.

More than 1.7 million migrants were taken into CBP custody during the fiscal year that ended in September, a record. CBP officials did not respond to a request for comment Thursday, a federal holiday. The agency generally refrains from comment on enforcement data before official release.

The Biden administration is facing calls from advocacy groups, rights organizations and some Democratic lawmakers to end use of the Title 42 public health authority, which allows the government to bypass normal immigration rules and rapidly return migrants. Title 42 expulsions are legally distinct from formal deportations and generally do not give asylum seekers the opportunity to apply for humanitarian protection.

U.S. authorities have expelled more than 1.3 million migrants using Title 42 since March 2020, government figures show.

Biden officials say they are committed to creating more pathways for Haitian migrants and others to work in the United States legally. On Monday the administration added Haiti to a list of countries eligible for temporary farm labor or seasonal work under the H-2A and H-2B visa programs.

Conditions in Haiti are dire. Armed gangs have been seizing control of neighborhoods and highways, cutting off deliveries of food and fuel. The State Department is warning travelers to avoid Haiti, citing an extremely high risk of kidnapping. “The Department of State urges U.S. citizens to make plans to depart Haiti now,” the U.S. Embassy in Port-au-Prince said in a security alert Wednesday.

Ramon said the deterrent effects of the expulsion flights are unlikely to last, particularly if economic conditions in Chile and Brazil don’t improve. “What we’re seeing could be a dip, as long as Haitians find themselves in problematic conditions that stay the same or get worse, so there is always the possibility another wave can happen.”

The abrupt decline in Haitian arrivals was offset somewhat by increases in migrants from other countries crossing the border, according to the CBP figures. More than 13,000 Venezuelans were taken into custody along the southern border last month, up 20 percent from September and more than double the number who arrived in August.

Fewer than 100 Venezuelans per month have been expelled under Title 42, data show, as strained relations between the U.S. government and the Maduro regime limit U.S. authorities’ ability to send flights there. Mexico does not have a visa requirement for Venezuelans to visit, so many have been flying to the Mexican cities of Tijuana and Mexicali, then walking across the U.S. border in the Yuma, Ariz. area.