US officials still cannot find the parents of 337 children separated at the Mexico-border by the Trump administration.

According to a new court filing released on Wednesday by the justice department and the American Civil Liberties Union, attorneys, activists and Biden officials have helped reunite 861 children with their parents but 337 remain in limbo.

In February, the Biden administration launched the Family Reunification Task Force as part of its efforts to undo the Trump administration’s controversial “zero-tolerance” policy that called for the criminal prosecution of adults crossing the border. The policy resulted in thousands of families being separated and received severe backlash from human rights organizations and immigration advocacy groups. Forty-five separated children have been reunited with their families since the creation of FRTF.

According to the filing, the 337 children fall into three groups. The first group consists of 250 children whose parents are believed to have been removed from the US after being separated from their children. The second group consists of approximately 75 children whose parents are believed to be in the US. The last group includes 12 children for whom the government has not provided a phone number for the parent, child, sponsor or attorney.

In addition to attempts to reach parents, sponsors and attorneys by telephone, the taskforce has also engaged in on-the-ground searches for the parents, which have been largely focused in the countries of origin of the parents who were removed from the US after their separation from their children.

Despite the government’s efforts to overhaul Trump’s “zero-tolerance” policy, Biden has warned migrants not to enter the US. In an interview with ABC in March, Biden said his message to migrants was: “Don’t come over. Don’t leave your town or city or community.”

According to Customs and Border Protection, the number of migrants that reached the southern border in July was more than 200,000, a figure that had not been seen in 20 years.

Among the 200,000 migrants was a “record” 19,000 unaccompanied minors, according to David Shahoulian, assistant secretary for border and immigration policy.