WASHINGTON — The Trump administration is unable to account for the whereabouts of nearly 1,500 migrant children who illegally entered the United States alone this year and were placed with sponsors after leaving federal shelters, according to congressional findings released on Tuesday.

The revelation echoes an admission in April by the Department of Health and Human Services that the government had similarly lost track of an additional 1,475 migrant children it had moved out of shelters last year.

In findings that lawmakers described as troubling, Senate investigators said the department could not determine with certainty the whereabouts of 1,488 out of 11,254 children the agency had placed with sponsors in 2018, based on follow-up calls from April 1 to June 30.

The inability to track the whereabouts of migrant children after they have been released to sponsors has raised concerns that they could end up with human traffickers or be used as laborers by people posing as relatives.