About 80 faith leaders from around the U.S. have signed a letter to President Barack Obama urging the government to stop detaining immigrant families, while high-ranking clerics visiting a South Texas detention facility Friday criticized the practice.

The U.S. government opened the detention centers, including two in Texas, in response to the tens of thousands of immigrants who crossed the U.S.-Mexico border last summer. Most were women with children or unaccompanied minors from Central America.

In their letter, released Friday, Christian and Jewish clerics decried the policy of detaining mothers and children as "inappropriate and unjust." Detention is harmful to children, they said, and leaves the mothers with diminished access to the legal system.

"These families are not a threat to our communities — they pose no risk to our safety and have committed no crimes. They themselves are fleeing real forms of terror, with a majority having valid asylum claims," the clerics wrote.

Archbishop Gustavo Garcia-Siller of San Antonio, along with four other Catholic and Lutheran bishops, toured the South Texas Family Residential Center in Dilley Friday, speaking with some of the 390 women and children housed there. The facility is expected to eventually hold 2,400 people.

The bishops said the women were upset about judges requiring them to post thousands of dollars in bonds for their release.

"If there was a theme to what I saw today it was tears, tears, tears. The people I spoke with had many tears," said Bishop Michael Rinehart, head of the Texas-Gulf Coast Synod of the Evangelical Lutheran Church.

U.S. Customs and Immigration Enforcement said in a statement that the centers are an important response to the surge in illegal immigration last summer and an effective and humane way to keep families together. ICE said its centers "operate in an open environment, which includes medical care, play rooms, social workers, educational services, and facilitate access to legal counsel."

Eusebio Elizondo, auxiliary bishop of the Roman Catholic Archdiocese of Seattle, said after the tour that he had seen mainly young mothers with very young children. He had seen no child older than 10, he said, and the youngest was a 9-month-old baby. Elizondo said he spoke with three women who reported feeling pressured to sign voluntary deportation documents before they could see a judge.

"If this is to send a message to other countries, I'm not sure that's effective because we have people still coming," said Rinehart. "I know it has been really effective to a distressing degree in separating families."

The bishops said their churches would be willing to help the immigrants if they were allowed to live in communities while their cases are processed.