The federal government is shutting down three temporary shelters that had been opened to house a surge of unaccompanied children from Central America entering the United States across the southern border, officials said Monday afternoon. The shelters at military bases in California, Oklahoma and Texas had provided housing for more than 7,700 children since they were opened in May and June. Tens of thousands of children have crossed the border with Mexico in recent months, setting off a political debate about what to do with the migrants and how quickly to send them back to their homes in El Salvador, Guatemala and Honduras. But officials at the Department of Health and Human Services, which shelters migrant children while their cases are pending, said the emergency shelters at the bases were no longer needed. "We are able to take this step because we have proactively expanded capacity to care for children in standard shelters, which are significantly less costly facilities," department officials said in a statement. "At the same time, we have seen a decrease in the number of children crossing the southwest border." The arrival of the children prompted President Obama to ask Congress for nearly $4 billion to care for the children while they are here and to process their refugee claims more quickly.