At least 18 infants and toddlers under two years old were separated from their parents at the border since late 2017 and had not been reunited with family as of June last year, according to a report on the Trump administration's "zero tolerance" policy released Friday by the House Oversight Committee.

Those children included nine infants under the age of one, the youngest of whom were four and five months old, according to the 32-page report from the Democratic-led committee. The children remained separated from their parents ranging from 20 days to half a year, according to the report. Ten of the children were from Honduras.

"The Trump Administration's child separations were more harmful, traumatic, and chaotic than previously known," the report said.

The committee said the data widely covers the 2,648 children separated from their parents after the "zero tolerance" policy of charging parents for illegal entry, thus separating them from their children, was announced in April of 2018.

The data does not include "information about thousands of additional children who may have been separated" prior to April of last year, children who were reunited with their parents prior to June 2018 and more than 700 children who have since been separated from their parents, the report said.

The data does include some children who were separated before the policy was officially announced.

Of the at least 18 infants and toddlers, the youngest was separated in February 2018, according to the report.

A Democratic committee aide told NBC News that of those 18 children, one was separated in late December 2017 and another was separated in early January 2018.

The report comes more than a year after the highly controversial Trump administration policy led to the separation of thousands of families as Democrats have continued investigating its impact. The report released Friday was based on information the committee received under subpoena and the committee said it has received some “but not all” of the information required by those subpoenas.

Last June, a federal judge ordered the Trump administration to reunify many of the separated migrant families. While many from the initial class in the lawsuit have been reunited, the case has since expanded to include potentially thousands more children separated before the policy was officially announced.

The Department of Health and Human Services said in an emailed statement that it "worked tirelessly with its inter-agency partners to comply" with the court's orders to "reunify parents and children separated under the zero tolerance" policy. The HHS stressed that it was not a law enforcement agency and "is not party to the child's immigration proceedings" and called on Congress to fix the broken system.

The Department of Homeland Security did not immediately respond to requests for comment.

The report also found that “many separated children were kept in government custody far longer than previously known,” including 25 held for more than a year, more than 50 held for six months to a year and at least 679 held for 46 to 75 days.

More than 400 children were moved to multiple Customs and Border Protection facilities and at least five were moved to multiple Immigration and Customs Enforcement facilities, according to the report. Almost 250 children were kept in CBP facilities longer than the 72 hours permitted by federal law, the report said.