Sen. Bob Casey says the Trump administration must quickly develop a plan to reunite parents and children who were separated at the southern border. Rather than putting people in jail, he added, officials could employ plenty of safe, secure alternatives to make sure they attend their immigration hearings.

"No American should support a policy that will lead to children having lifelong [emotional and physical] damage because of some political decision in Washington," the Pennsylvania Democrat said during a Monday news conference in Philadelphia.

He described the practice of separating migrant children from parents, rescinded by the president last week, as "a policy that is straight from the pit of hell."

An estimated 2,500 children have been separated from their parents as a result of the administration's "zero-tolerance policy," in which all those who arrive at the border without papers are referred for criminal prosecution. At least several dozen children are being held in Pennsylvania while their parents or grandparents await criminal prosecution for illegally entering the United States.

Last week, amid a national outcry, the president signed an executive order to end that practice, which he had long blamed on the Democrats. The first steps at reunification have been slow and confusing, according to immigration advocates.

About 500 children have been reunited with their parents, Casey said, but roughly 2,000 are still separated. He urged the Trump administration to reexamine its zero-tolerance policy, which he called "the root of evil here."

Casey spoke at 30th Street Station surrounded by about a dozen physicians, child advocates and supporters who decried what they said were lasting, harmful health impacts on children who are kept from their parents.

The government must "make sure our border is secure," Casey said, but the jailing of children, parents or families should be replaced by more humane and less expensive options.

For instance, many people come to the United States seeking asylum — a legal means of entering the country, often to escape persecution in their homelands. They want hearings. They need not be physically detained, Casey said, when they could be monitored by phone or at work sites.

The zero-tolerance policy announced by U.S. Attorney General Jeff Sessions in May resulted in parents being held in one facility, their children moved elsewhere. News reports of weeping children snatched from their mothers and fathers led to wide criticism of the administration by church groups, politicians and children's advocates.

This article contains information from the Associated Press.