Federal officials have yet to explain how they’ll reunite more than 400 migrant children with the parents who were deported without them — “unacceptable” news for the judge who had ordered the government to have done so already.

In a court filing this week, the government said the burden for reunifying families should fall on the American Civil Liberties Union, the advocacy group that successfully sued to order the reunifications, though the government would “facilitate communications.” The ACLU shot back that the government “must bear the ultimate burden of finding the parents” because “it was the government’s unconstitutional separation practice that led to this crisis.”

In addition to the 410 parents who’ve been deported, the government has yet to locate 68 parents released into the United States.

Bickering over the reunifications continued at a court conference in San Diego on Friday, where U.S. District Judge Dana Sabraw told Department of Justice lawyers he found their submission “disappointing.”

“The reality is there are still close to 500 parents that have not been located. … All of this is the result of the government’s separation, and then inability and failure to track and reunite,” Sabraw said. “For every parent who is not located, there will be a permanently orphaned child. And that is 100 percent the responsibility of the administration.”

It was the first time Sabraw had publicly acknowledged the possibility that the government’s family separation policy could leave some children without their parents permanently. That outcome would leave them in the care of the federal government, which cares for about 12,000 unaccompanied migrant children, some of them in shelters with troubling histories.

The ACLU and other advocacy groups have already mobilized to locate deported migrant parents, most of whom, ACLU lawyer Lee Gelernt said, are in Honduras or Guatemala.

The challenge for the nonprofit and advocacy groups searching for them is the little information they have about those parents’ whereabouts. For some parents, Gelernt said, advocates have only a street listed, with no number. For others, the only address information listed is a city of several hundred thousand people.

The government, Gelernt said, has further files on the parents — including, in many cases, a contact phone number — that it has yet to produce. The government has resisted providing further information; doing so, DOJ attorney Scott Stewart said, would be “burdensome.”

But Sabraw told the government to provide that information to the ACLU by Aug. 10, and made it clear that he expects further efforts from the federal officials.

“This responsibility, of course, is 100 percent on the government,” he said.

The judge asked the government to designate one point person to oversee the process, and Stewart demurred, saying that’s something the government “should look into.”

Then, the judge asked the ACLU to appoint a steering committee to facilitate its efforts. The ACLU, Gelernt replied, has already done that.