(CNN) In a new court-ordered effort to identify potentially thousands of additional immigrant families that the US government separated at the southern border, more than 1,700 cases of possible separation have been found so far.

Cmdr. Jonathan White of the US Public Health Service Commissioned Corps says 1,712 cases with "some preliminary indication of separation" have been referred to US Customs and Border Protection for the next phase of review out of the initial pool of 4,108 children's case files that corps officers combed through.

Some of those cases ultimately might not involve separations, White said Friday in a federal court hearing.

"What we transmit to CBP is solely those cases that have some preliminary indication of separation," White said. "We err on the side of inclusion."

The new effort to track down parents and children who were split up at the border is the latest chapter in the ACLU's lawsuit over family separations.