The first cohort of migrants enrolled in a newly revived border program requiring asylum-seekers to wait out their court cases in Mexico had their U.S. immigration hearings in Texas on Monday, according to senior administration officials.

The group of 36 migrants were returned to Mexico under the so-called Remain in Mexico program, or the Migrant Protection Protocols, which requires migrants who request U.S. protection to wait in Mexico for decisions in their immigration cases. The Biden administration revived the Trump-era program last month under court order, though it has continued to fight that ruling in court.

On a call with reporters Monday, the administration officials said the program, previously limited to migrants who crossed into El Paso, Texas, will be expanded to the San Diego port of entry, where individuals would be pushed back into Tijuana, Mexico.

One official said the administration plans to expand the program to additional ports of entry “in the near future,” and they “are actively discussing the timing and logistics of those expansions with the government of Mexico.”

More than 200 migrants have been sent back to Mexico under the reinstated program, according to a spokesperson for the United Nations International Organization for Migration.

The administration officials stressed current efforts to address humanitarian concerns raised during the Trump administration’s implementation of the program, such as giving the migrants COVID-19 vaccines and offering legal orientation programs.

Individuals who express a fear of persecution at their court hearings will be sent to a Border Patrol facility, where they will have 24 hours to consult with a lawyer before undergoing a screening with an asylum officer. The Mexican government will also provide migrants under the program access to shelters and safe transportation, the officials said.

Still, the Biden administration has drawn backlash from Democratic lawmakers and advocates alike over its revival of the program.

Researchers with Human Rights First have documented more than 1,500 publicly reported instances of rapes, murders, kidnappings and other attacks against migrants pushed back to Mexico under the program while it was in effect under the Trump administration.

In December, a bicameral group of more than three dozen Democratic lawmakers took particular issue with the Biden administration’s decision to expand the policy to more nationalities than the prior administration did, as well as to provide asylum-seekers with only 24 hours to consult with a lawyer before their screenings.

“These choices suggest that your Administration has made a decision to normalize and expand a cruel ‘deterrent’ policy that fails to actually address the root causes of migration,” the lawmakers wrote in a letter to President Joe Biden and Homeland Security Secretary Alejandro Mayorkas.

Earlier this year, dozens of legal services programs and law school clinics publicly said they would refuse to offer their legal services to migrants in the program should the administration resume it. They argued there was “no way to make this program safe, humane, or lawful” and that they “refuse to be complicit” in it.

On Monday’s call, the administration officials called on those legal services providers to “step up” and represent these migrants in the program. One official said they have been “encouraged by many of the conversations” they have had with providers so far.

“We are certainly hopeful that over time that more and more organizations and individuals and entities will step up to provide the representation that we all know is so critically needed,” the official said.