High-ranking U.S. Senate Democrats have called on the Obama administration to reverse its new policy of detaining Central American immigrant families, warning it could be damaging to the young children being housed in the facilities.

Senate Majority Leader Harry Reid of Nevada, Senate Judiciary Committee Chairman Patrick Leahy of Vermont and eight other Democrats wrote Department of Homeland Security Secretary Jeh Johnson on Thursday to complain about the detentions.

"Mothers and their children who have fled violence in their home countries should not be treated like criminals," wrote the senators, who also included Democratic leadership members Dick Durbin of Illinois, Charles Schumer of New York and Patty Murray of Washington state.

The detention policy, which was initiated this past summer as tens of thousands of families and unaccompanied children rushed to the U.S. border, is part of a broader White House strategy of deterring another influx next year.

Many of the migrants are fleeing El Salvador, Honduras and Guatemala, where gang violence, drugs and human trafficking are rampant.

In 2009, the United States stopped housing newly arrived immigrant families in a troubled Texas detention facility. Instead, the Obama administration made less restrictive measures, such as ankle bracelets, telephone interviews and other monitoring programs the centerpiece of its policy for keeping tabs on migrants awaiting court determinations on their status.

But that changed a few months ago, as President Barack Obama was under intense pressure from Republicans in Congress to stop the record numbers of children and families seeking refuge in the United States and arriving without visas.

He responded by directing the opening of family detention centers, expediting immigration court cases, refusing bond for many of the migrants and working with Mexico to secure borders.

By year's end, the federal government will have the capacity to detain about 4,000 mothers and children at any one time in centers located in New Mexico, Texas and Pennsylvania.

Last month, the administration announced plans in coming months to open a second Texas facility, with 2,400 beds, to augment the three existing centers. Human rights and immigrant advocacy groups have criticized the move.

"We are troubled by your apparent decision to make permanent and greatly expand the policy of family detention" amid reports of problems caring for the detainees, the senators wrote.

In their letter, the senators also referred to problems detainees were having getting legal representation and the "rushed nature" of legal proceedings that could lead to the return of migrants to dangerous situations in their home countries.

Following the Nov. 4 congressional elections, Congress is expected to debate a budget bill that would contain funds for agencies tasked with handling the immigrant families. It was unclear whether the high-ranking Democratic senators will try to withhold future funding for the detention facilities.

Besides the controversial family detention centers, the government maintains more than 30,000 beds to detain adult immigrants awaiting decisions on whether they can stay in the United States.

(Reporting by Richard Cowan; Editing by Lisa Von Ahn)