The Senate Judiciary Committee is demanding answers from federal immigration officials about the Trump administration's separation of migrant children from their families and its struggle to reunite them, a fraught effort that's drawn election-year criticism from both parties.

But a hearing scheduled for Tuesday on the topic may have a wider focus after the committee's bipartisan leaders asked federal investigators to probe reports of sexual and other abuse of immigrants at government detention facilities.

Committee Chairman Chuck Grassley, R-Iowa, and top Democrat on the panel, Dianne Feinstein, of California, asked late Monday for an examination of alleged sexual, physical and emotional mistreatment of immigrants held at agency facilities, saying the problems may have been occurring since 2014 or earlier.

With President Donald Trump already under fire for taking thousands of migrant children from their detained parents — and botching the reunification of many — the request for the investigation elevated yet another issue to the administration's list of immigration headaches.

"These allegations of abuse are extremely disturbing and must be addressed," Grassley and Feinstein wrote in a letter to the departments of Homeland Security and Health and Human Services. "This is not a partisan issue, as reporting suggests, many have been occurring for years. Immigrant families and children kept in federal custody deserve to be treated with basic human dignity and respect and should never be subjected to these forms of abuse."

The hearing also comes as Trump has once again threatened to shut down the federal government as Congress has yet to formally act on providing legislation to address outstanding immigration issues. Trump cites lack of support for funding his border wall as an area of contention -- telling U.S and visiting reporters from Italy on Monday that he would have "no problem" with shutting down the government over immigration disputes on Capitol Hill. 

Officials from U.S. Immigration and Customs Enforcement, the Border Patrol and other agencies are testifying before the Senate Judiciary Committee.

(CBS News)