The Biden administration is reviewing the cases of 5,600 migrant children to see whether they were separated from parents at the U.S.-Mexico border under former President Donald Trump, a Department of Homeland Security official said on Wednesday.

The review is expected to find a small number of additional separations on top of thousands identified through ongoing litigation, the official told reporters.

President Joe Biden, a Democrat who took over from the Republican Trump on Jan. 20, issued an executive order in February to create a task force to reunite children and parents still separated by Trump's "zero tolerance" border strategy.

Thousands of children were separated from their parents at the southwestern U.S. border under the policy, which charged parents with federal immigration offenses and sent them to jails, while children were labeled “unaccompanied” and placed in shelters.

The Biden administration task force has yet to reunify any of the separated families, the DHS official told reporters on Wednesday, requesting anonymity to discuss the matter.

Parties in a lawsuit over the separations have been unable to reach the parents of more than 500 children subject to the separations.