The Biden administration is preparing to send planeloads of migrants back to Haiti starting as soon as Sunday in a deportation blitz aimed at discouraging more border-crossers from streaming into a crude South Texas camp where nearly 15,000 have arrived, according to five U.S. officials with knowledge of the plans.

The Department of Homeland Security said it would not discuss the frequency and schedule of the flights, citing operational security. But one official said DHS will start with up to three flights per day, while cautioning that plans remained in flux.

Marsha Espinosa, a spokeswoman for the department, confirmed the plans in an email.

“DHS will secure additional transportation to accelerate the pace and increase the capacity of removal flights to Haiti and other destinations in the hemisphere within the next 72 hours,” Espinosa said.

“We have reiterated that our borders are not open, and people should not make the dangerous journey,” Espinosa added. “Irregular migration poses a significant threat to the health and welfare of border communities and to the lives of migrants themselves and should not be attempted.”

Haitian authorities have agreed to accept at least three flights per day, but Biden officials want to maximize deportations to break the momentum of the massive influx into the encampment in Del Rio, Tex., said a second official who, like others, spoke on the condition of anonymity because they were not authorized to speak to reporters.

Biden officials have discussed sending as many as eight flights per day, which typically carry 100-120 deportees.

Another U.S. official involved in the planning insisted that the flight operation was not a targeted measure aimed at Haitians, but was the application of U.S. immigration laws allowing the government to swiftly remove border crossers who arrive in the country illegally.

“This isn’t about any one country or country of origin,” the official said. “This is about enforcing border restrictions on those who continue to enter the country illegally and put their lives and the lives of the federal workforce at risk.”

The Biden administration continues to use a pandemic enforcement measure known as Title 42 to rapidly “expel” border crossers to Mexico or their home countries. Officials said some of the flights to Haiti probably would be expulsion flights relying on the public health authority of the Title 42 provision.

A federal judge on Thursday blocked the Biden administration from using Title 42 to expel migrant families but stayed the order for 14 days. The Biden administration appealed the ruling Friday.

By announcing its intent to deport the Haitians before launching the flights, Biden officials also appeared to be hoping that some in the camp would abandon their attempt to remain in the United States and return to Mexico. Migrants arriving at the camp have been given numbered tickets by the U.S. Border Patrol as they await their turn to be formally taken into U.S. custody, normally the first step in starting the process of requesting U.S. asylum or some other form of protection from deportation.

Some Haitians seeking to avoid deportation could abandon the Del Rio camp and try to abscond in the United States or return to Mexico, two U.S. officials acknowledged.

Many of the migrants crowded under the highway bridge are part of a larger wave of Haitians that arrived in Brazil, Chile and other South American nations after their country’s devastating earthquake in 2010.

DHS officials said in a statement Saturday that they would send at least 400 additional Border Patrol agents and other personnel to Del Rio “to improve control of the area.”

Authorities are transferring some of the migrants to other areas of the border to ease pressure on the camp, the statement said, with 2,000 relocated Friday.

The statement said DHS officials are taking “urgent humanitarian actions” to reduce crowding at the camp and improve security conditions, “including having Border Patrol emergency medical technicians on hand and providing water, towels, and portable toilets.”

The Biden administration also is “working with source and transit countries in the region to accept individuals who previously resided in those countries,” an apparent reference to the South American nations where many of the migrants initially settled.

The White House has directed federal agencies to help Haiti and other governments in the region to prepare for a surge of returnees, DHS said.

Immigrant advocates and some Democrats have been calling on Biden to suspend all deportation flights to Haiti after the country’s president was assassinated in July and a 7.2-magnitude earthquake last month killed at least 2,000.

“The Biden Administration cannot claim it is doing everything it can to support the Haitian community while continuing to unjustly deport Haitians as the island weathers its worst political, public health and economic crises yet,” said Rep. Ayanna Pressley (D-Mass.), the co-chair of the House Haiti caucus, in a statement Friday.

“We have a moral obligation to lead with compassion,” she said.

The Biden administration has extended a form of provisional residency known as temporary protected status to eligible Haitians who arrived in the United States before May, and the administration paused deportation flights after the August earthquake, which have since resumed.

The new deportation flights plan is likely to outrage advocates, but it points to the Biden administration’s hardening view of immigration enforcement after months of surging migration levels.

Last month, U.S. authorities took more than 208,000 migrants into custody on the southern border, the latest U.S. Customs and Border Protection figures show, as illegal crossings reached their highest levels in more than two decades.