Washington (CNN) A report from the US Government Accountability Office released Wednesday describes chaos and confusion among federal agencies this past summer over efforts to reunify undocumented children separated from their parents at the US-Mexico border.

According to the report, officials at the department of Homeland Security and Health and Human Services "did not plan for the potential increase in the number of children separated from their parent or legal guardian as a result of the Attorney General's (Jeff Sessions) April 2018 'zero tolerance' memo."

A similar report from the DHS Inspector General released earlier this month found that the agency was not fully prepared for the zero-tolerance memo.

The officials interviewed by the GAO also said they "were unaware of the memo in advance of its public release."

The Justice Department memo called for the prosecution of all individuals caught coming into the United States illegally. It led to more migrant children being separated from their parents when children entering the country with their parents were placed into custody with a sponsor, in foster care, or held in a shelter as their parents were detained separately.

News of migrant family separations by American immigration authorities reached a fever pitch this summer following the issuance of the zero-tolerance memo.

The policy was essentially put on hold in June

According to the new GAO report, which included interviews with staff during visits to Office of Refugee Resettlement shelters in Arizona and Texas, the departments did not take specific steps to prepare for the increase in children referred to shelters.

According to DHS and HHS officials, once the families were separated, staff faced challenges coordinating communication between family members.

"DHS and HHS officials told us that they facilitated telephone conversations between parents and their children. However, even though a call had been scheduled, DHS and HHS officials said there were instances when either the parent or the child was unavailable to talk," the report states. "In addition, ORR shelter staff told us it was difficult contacting (Immigration and Customs Enforcement) detention centers and reaching the detained parents, especially when trying to establish the first contact."

One refugee resettlement field staff person told the GAO "that ICE personnel monitoring the phone calls between parents and children began terminating calls when they heard her speaking, explaining that the call was supposed to be between the child and the parent only."

"She said this was problematic because it inhibited her ability to determine if there were questions regarding parentage, parental fitness, or any possible danger to the child. According to ICE officials, they were concerned that ORR staff were consuming too much of the 10 minutes allotted for parents and children to speak and were also going over the allotted time. As a result, there was less time available for other parents to speak with their children in ORR custody," the report relays.

The report also details challenges HHS faced with family reunification, "including children having to wait for parents for unreasonably long amounts of time and parents transported to the wrong facilities."

"Shelter staff we interviewed also told us there were times when the parent was not available because the parent was in transit, resulting in long waits for the children and the accompanying shelter staff. In one case, staff at one shelter told us that they had to stay two nights in a hotel with the child before reunification could occur," the report states.

Refugee resettlement officials said that HHS leadership advised them not to plan for continued increases "since DHS officials told them that DHS did not have an official policy of separating parents and children."

The report investigated the process to coordinate data systems from DHS and HHS, which "did not systematically collect and maintain information to indicate when a child was separated from his or her parents" prior to the zero-tolerance memo.

Between April and August 2018, the report states, the agencies updated their data systems "to help notate in their records when children are separated from parents." Within DHS, the agency "made changes to their data systems to allow them to better indicate cases in which children were separated from their parents."

Despite making those changes, "ORR officials stated, as of early September 2018, they were unaware that DHS made these systems changes."

The report indicated that though data systems were updated this year to better indicate whether a migrant child has been separated from their parent, "it is too soon to know the extent to which these changes, if fully implemented, will consistently indicate when children have been separated from their parents, or will help reunify families, if appropriate."