The Trump administration may have taken “thousands” more immigrant children from parents and guardians at the border than was previously known, and does not know how many families were separated in total, according to a report released Thursday by the inspector general of the Department of Health and Human Services. The government also does not know if these families were reunified.

This group is in addition to the 2,737 children the government separated from their parents starting last April, as part of a “zero tolerance” policy that required all migrants to be criminally prosecuted after crossing the border.

In the summer of 2017, staff and officials from the Office of Refugee Resettlement (ORR), which runs the government shelters for unaccompanied migrant children, saw a “steep increase” in the number of separated children.

According the inspector general’s report, these children were “often very young” and required “placement at specially licensed facilities,” which resulted in a shortage of beds.

The report does not specify the exact number of kids who were separated from their parents and guardians because ORR staff were only informally tracking the issue, nor does it explain why these children were taken from their families. It’s likely impossible for the government to determine the full scope of how many migrant kids the Trump administration has taken away from their parents.

John Moore via Getty Images A boy and father from Honduras are taken into custody by U.S. Border Patrol agents near the U.S.-Mexico Border on June 12, 2018, near Mission, Texas.

Michelle Brané, the director of migrant rights and justice at the Women’s Refugee Commission, said that her organization noticed an uptick in the number of family separations during 2017 and filed a complaint about the practice to the Department of Homeland Security, along with other immigrant rights groups.

Brané did not see an explicit policy during that time about taking children away from their parents at the border, but the administration was sending “plenty of messages” to staff in support of the practice, she said.

In March of 2017, then-Secretary of Homeland Security John Kelly told CNN the department was considering family separation. From July to October of that year, the Trump administration ran a “pilot program” to test a “zero tolerance” policy in El Paso.

“We have been saying [this administration was] separating kids long before ‘zero tolerance,’” said Brané. “A lot of children were not counted in that snapshot.”

Katie Waldman, a DHS spokeswoman, told HuffPost in a statement: “It was and continues to be standard for apprehended minors to be separated when the adult is not the parent or legal guardian, the child’s safety is at risk or serious criminal activity by the adult. ... For the HHS OIG to claim it was not known that DHS is actively enforcing this policy in the same manner for more than a decade children were placed in HHS custody, casts doubt on the HHS OIG’s credibility on this topic.”

The public and political outcry against Trump’s “zero tolerance” policy was so strong that the president signed an executive order to stop family separation in June. And this new report has re-stoked anger over a cruel practice that dehumanizes immigrants.

“The Trump Administration’s family separation policy is more than a bureaucratic lapse in judgment. It is and was a cruel policy inconsistent with the values of this nation,” said Senator Dick Durbin (D-Ill.) in a statement. “It’s inconceivable that the government of the United States chose to secretly separate thousands of children from their parents or guardians, was unable or unwilling to reunite these families for months due to incompetent leadership and poor planning, and still doesn’t know how many children were separated.”

We have been saying [this administration was] separating kids long before ‘zero tolerance.' Michelle Brané, the director of migrant rights and justice at the Women’s Refugee Commission

Durbin also called for Homeland Security Secretary Kirstjen Nielsen to resign.

In Ms. L v. ICE, an ACLU lawsuit that required the Trump administration to reunite separated children with their parents, the organization also criticized the government for failing to properly keep track of separated families, which forced immigration advocates to find the locations of hundreds of deported parents themselves.

According to the inspector general’s report, 159 children who were separated under “zero tolerance” are still in ORR care. More than half of these children’s parents were deported and opted to keep their kids in the U.S. because of the life-threatening situations they fled back in Central America.

“This report reaffirms that the government never had a clear picture of how many children it ripped from their parents,” said Lee Gelernt, lead attorney and deputy director of the ACLU’s Immigrants’ Rights Project in a statement. “We will be back in court over this latest revelation.”

Brané says the fact that the Trump administration both takes children from their parents and then fails to properly track those separations shows a cruel indifference to immigrants.

“It shows an extreme disregard for people’s rights and for the safety of children,” she said. “This administration doesn’t see these families and children as people who deserve consideration.”

This story has been updated with a statement from a DHS spokeswoman.