More than a dozen United States senators, including the Democrats' nominee for vice president, are calling on the Obama administration to close the Berks Family Residential Center.

The facility in Bern Township houses women and children who are seeking asylum hearings.

In a letter to Homeland Security Secretary Jeh Johnson, the lawmakers noted that women and children as young as two years old have been detained for nearly a year or longer.

The letter expresses concern that some detained children are exhibiting signs of serious health problems and psychological harms associated with prolonged detention.

"Detention of families should only be used as a last resort, when there is a significant risk of flight or a serious threat to public safety or national security that cannot be addressed through other means," the senators stated in their letter. "We urge you to review these cases individually and release these children with their mothers immediately unless there is compelling evidence that they pose a specific public safety or flight risk that cannot be otherwise ameliorated through alternatives to detention."

The letter, led by Sen. Patrick Leahy, a Vermont Democrat, and Sen. Mazie Hirono, a Democrat from Hawaii, came after world leaders met in New York for the United Nations Summit for Refugees and Migrants.

In addition to Leahy and Hirono, the letter was signed by Sen. Dick Durbin of Illinois; Sen. Patty Murray of Washington; Sen. Robert Menendez of New Jersey; Sen. Elizabeth Warren of Massachusetts; Sen. Bob Casey of Pennsylvania; Sen. Cory Booker of New Jersey; Sen. Tim Kaine of Virginia, the Democratic vice presidential nominee; Sen. Kirsten Gillibrand of New York; Sen. Edward Markey of Massachusetts; Sen. Al Franken of Minnesota; Sen. Bernie Sanders of Vermont; Sen. Michael Bennet of Coloardo; Sen. Ben Cardin of Maryland; Sen. Sherrod Brown of Ohio; and Sen. Tammy Baldwin of Wisconsin.

Make the Road Pennsylvania, a grassroots advocacy organization representing Latino communities in Berks County and elsewhere in Pennsylvania, on Friday applauded the senators for their letter.

"There is no defense for the continued unjust, and illegal in Pennsylvania, incarceration of families seeking asylum at the Berks Detention Center," said Adanjesus Marin, the group's director.

Bernie Sanders, then a candidate for the Democratic presidential nomination, called for the center's closure during a campaign rally in Reading in April.

"The government should not be in the painful and inhumane business of locking up families who have fled unspeakable violence in Honduras, Guatemala, El Salvador and other countries throughout the world," Sanders told his supporters. "Instead, we should treat these families with the compassion, the dignity and the respect they deserve."

Bob Casey, a Pennsylvania Democrat, has also expressed his concerns about the detention center in a letter he wrote to Johnson in August.