The Trump administration said in a court filing that it may have deported 463 parents without their children as part of the “zero tolerance” immigration policy on the southern border, according to a report.

Administration officials said the 463 cases were “under review” in a progress report sent on Monday to US District Judge Dana Sabraw, meaning the number of children separated from their parents might be higher than originally thought, the Washington Post said.

Sabraw gave the administration a 30-day deadline, which expires Thursday, to unite as many separated families as it can.

Last week, he ordered the government to clarify how many of the 2,500 parents eligible to be reunited with their children are no longer in the country.

Sabraw also temporarily suspended the deportations of families no longer separated.

An attorney for the ACLU, which has sued the Trump administration over the separations, lauded the government for trying to come up with a tally, but cautioned that the numbers could raise more concerns.

“If this number turns out to be as large as the report suggests, this is going to be a big issue for us,” Stephen Kang told the Washington Post. “We have a lot of questions.”

The government, according to the court filing, has reunited 879 parents with their children, up from 450 on Friday, and another 538 parents have been approved to be reunited, meaning that half of the separated families could be back together by the deadline.

The families were separated after Attorney General Jeff Sessions announced the “zero tolerance” policy in May, requiring that all adults crossing the border illegally be prosecuted.

While in custody, they must be separated from their children.

After facing intense criticism on the policy, President Trump signed an executive order on June 20 stopping the separations but continuing the criminal prosecutions for “improper entry.”