At least 18 migrant children under age 2 were separated from their parents at the U.S.-Mexico border for a period of “20 days to half a year,” according to a new report from the House Oversight and Reform Committee.

Nine of the children were infants under age 1.

The report, released Friday, looked at the effect the Trump administration’s “zero tolerance policy” had on families arriving at the border, largely seeking asylum, over a period of months in 2018. Beginning in April 2018, the policy led to the separation of thousands of families, provoking nationwide outrage and protests. Although the administration backed off its “zero tolerance policy” in June 2018, some separations have continued.

Records used to compile the information “did not fully specify” whether the person to whom a child was released was a parent, other relative or a nonrelative sponsor, the report noted.

A January report by a government watchdog group concluded that the Trump administration does not know how many children it has separated from their parents. The House committee now says it has obtained new information on at least 2,648 children who were separated last year, concluding that the separations have been “more harmful, traumatic, and chaotic than previously known.”

At least 241 of the separated children were kept in Customs and Border Patrol facilities “longer than the 72 hours permitted by law,” with more than 50 held for six months to a year, and more than 25 held for more than a year.

More than 400 of the children were moved to “multiple” CBP facilities, the report said, and more than 80 children were moved to multiple facilities run by the Office of Refugee Resettlement for unaccompanied minors. At least five children were moved to multiple Immigration and Customs Enforcement facilities.

After being reunited, many of the families continued to be detained for months, even though the Supreme Court determined in 1993 that child detainees should be held for no more than 20 days.

The report was released shortly before the House committee convened a Friday hearing on conditions at the border, with Reps. Alexandria Ocasio-Cortez (D-N.Y.) and Rashida Talib (D-Mich.) set to speak about the border facilities they toured last week that have been labeled as concentration camps by some.

At least three children have died in CBP custody since December, as officials remain overwhelmed by the influx of migrants fleeing poverty and violence in Central America.

Department of Homeland Security Secretary Kirstjen Nielsen was ousted in April over President Donald Trump’s frustration with her response to the chaotic conditions at the border and has not yet been permanently replaced. Kevin McAleenan is currently serving as acting secretary.