The U.S. government is expected to arrange the reunification this week of four migrant families who were separated during the Trump administration as part of President Biden’s effort to make amends to parents and children affected by a policy he has decried as cruel.

Homeland Security Secretary Alejandro Mayorkas said the Biden administration will allow a small group of parents to enter the U.S. legally this week to reunite with their children, who have been living in the U.S. since their forced separations. During a call with reporters on Sunday, Mayorkas called the Trump-era separations a “tragedy.” 

“The first families reuniting this week are mothers. They are sons. They are daughters. They are children who were three-years-old at the time of separation. They are teenagers who have had to live without their parents during their most formative years,” Mayorkas added.

Among them are two mothers from Mexico and Honduras who have not seen their children since late 2017, according to Mayorkas. 

The reunifications will be the first to occur in the U.S. under Mr. Biden, who created a Mayorkas-led task force in February to locate and reunite separated migrant families. The task force focused its early work on collecting and reviewing troves of documents related to the family separations that occurred under the former President Trump.

The Biden administration’s decision to grant humanitarian parole to parents deported without their children is a stark departure from the stance taken by the Trump administration, which refused to allow the families it separated to reunite on U.S. soil. The Trump administration did allow fewer than a dozen parents to reunite with their children in the U.S., but only after a federal court ordered it to do so.

“We are very excited that these parents will finally be able to hug their children after years of forced separation,” Lee Gelernt, the American Civil Liberties Union (ACLU) lawyer representing separated families in a federal court case, told CBS News. “But we are not about to celebrate given that there are thousands of families who need help.”

Gelernt said he has been negotiating with the Biden administration over how to reunite an estimated 1,000 additional families the ACLU estimates remain separated. He is also urging the administration to place families affected by the Trump-era separations on a pathway to U.S. citizenship and provide them social services and compensation “for the deliberate abuse they suffered at the hands of the Trump administration.”

During the call with reporters Sunday, Michelle Brané, the family reunification task force’s executive director, said the administration is looking at securing “longer-term status” for affected families. 

About 2,800 migrant families were separated in the spring of 2018 when the Trump administration implemented its “zero tolerance” border crackdown across the entire U.S.-Mexico border. Parents were generally prosecuted for crossing the border illegally, while their children were incorrectly designated as unaccompanied minors and sent to government-overseen shelters.

That border-wide policy, which officials said was designed to deter unauthorized migration, ended in June 2018 after a massive public uproar forced Mr. Trump to discontinue the mass separations. A federal judge also blocked the practice and ordered the administration to reunite the families it had separated.

More than 1,500 migrant families were split up in late 2017 and early 2018 before “zero tolerance” became a formal policy. Many parents were deported without their children during that time. As of April 7, advocates had yet to locate the parents of 445 children, according to a federal court filing.

While the Department of Homeland Security has taken a lead role in the task force, other departments have also contributed to its efforts. The Department of Health and Human Services has been charged with offering social services to families, while the State Department has been facilitating travel documents so parents and children can reunite in the U.S.

Mayorkas on Sunday said the task force is committed to reuniting “many more” families in coming months.

“Our team is dedicated to finding every family and giving them an opportunity to reunite and heal,” Mayorkas said.