The U.S. government will update a federal judge on Tuesday about its efforts to meet a Thursday deadline for reuniting roughly 2,500 immigrant children and parents who were separated by officials as they crossed the U.S.-Mexico border.

As of Monday, at least 879 parents had been reunited, although 463 may have been deported without their child, making it unclear when those parents will be back with their child, according to a joint court filing by the government and the American Civil Liberties Union.

The Trump administration ordered the families separated in May as part of a “zero tolerance” policy meant to discourage illegal immigration.

President Donald Trump ended the practice in late June after video footage of children sitting in cages and audio of wailing kids sparked international outrage.

U.S. Judge Dana Sabraw in San Diego ordered last month that the government had to reunite the children by Thursday in a case that was brought by the ACLU.

The judge may use Tuesday’s hearing to consider a request by the ACLU that parents facing final removal orders not be deported for at least a week after being reunited with their children. The rights group said the time was necessary for the parents to consider the legal options for their children, who might be better off remaining in the United States to pursue asylum. Most of the parents fled violence in Guatemala, Honduras and El Salvador.

The reunification process has been marred by disarray within government agencies, difficulty tracking adults and children in detention and a lack of communication with advocates for immigrants.

The government reunited children under 5 earlier this month, although it missed a court-ordered deadline for doing so, which it blamed partly on procedures such as parental background checks to ensure the security of children.

Sabraw has criticized the government for needless safety measures that never would have been applied if the families had not been separated by the government.

In the past week, the judge said he has been encouraged by signs that the government was placing more emphasis on meeting the reunification deadline.

Reporting by Tom Hals in Wilmington, Delaware; Editing by Sue Horton and Lisa Shumaker