Over 500 children have yet to be reunited with their parents after the Trump administration began separating migrant families in 2017, Buzzfeed News reports. On Tuesday (Oct. 20), lawyers who have been tasked with reuniting the families said they’ve been unable to find the parents of 545 children and that their efforts have been slowed by the pandemic.

“People are constantly asking me when we will find all the families and I unfortunately do not know,” lead attorney and ACLU Immigrants’ Rights Project Deputy Director Lee Gelernt told the outlet. “The numbers tell one story, but each individual child has his or her own story with its own human dimension and that’s why we cannot stop looking until we have found every family.”

Tuesday’s court filing stems from a lawsuit that the ACLU filed back in February of 2018. The suit was filed on the behalf of a Congolese asylum-seeker — identified as “Ms. L” — who had been separated from her 7-year-old daughter. That year, U.S. immigrant authorities broke up families as part of Trump’s “zero tolerance policy” on immigration. Parents were sent to federal prison before being prosecuted for entering the country without authorization, while their children were taken into custody by the Office of Refugee Resettlement.

Ms. L was reunited with her daughter, but the case has since expanded into a class-action lawsuit to include another 1,030 children who were separated from their parents. As of Tuesday, a committee designed to reunite the families has successfully tracked down parents of 485 children. However, the ACLU believes about two-thirds of the parents they have not been able to reach were already deported to their home countries.

“The contact information the government gave us was largely stale, so we’ve been looking for the families on the ground in Central America,” Gelernt said. “But because of COVID, the on the ground search has halted.”

Speaking with Buzzfeed, the attorney further described the situation as “extremely sad,” adding that some of the children — who were torn from their families as babies — “have now spent more than half their lives separated from their parents.” During that time, the kids have lived with American sponsors that Gelernt said range from close relatives to foster families.

Although the on-the-ground search was temporarily suspended due to COVID-19, Tuesday’s filing reports that the efforts will now start back up again.

“The Steering Committee intends to continue physical on-the-ground searches while it remains safe to do so, and will continue to update the Court on its progress, particularly if such searches must be limited or suspended again due to travel restrictions or health risks,” the report reads.