UPDATE: Casey released the letter publicly Monday evening.

Sen. Bob Casey of Pennsylvania has drafted a letter to send this week to the U.S. Homeland Security secretary urging “the immediate release of four children and their mothers who are being detained at the Berks County Residential Center.”

Eight other Democratic senators, including former presidential candidate Bernie Sanders, and 13 U.S. representatives from across the country are also expected to sign Casey’s letter to Secretary John F. Kelly. The list of co-signers was not final as of Monday morning and could grow, according to an official with knowledge of the letter.

“With more pressing issues facing ICE and the need to spend our limited federal resources wisely, there are more cost effective and humane approaches to this situation than family detention,” the letter, which could be sent as soon as Monday, reads. “The Department of Homeland Security should be focused on apprehending and deporting violent felons and maintaining a secure border, rather than expelling young mothers and children fleeing near certain death in their home countries.”

The Berks County facility is one of only three detention centers in the country for undocumented immigrant families. The other two are in Texas. The facility, which is run by the county and paid for with federal funds, was scheduled to lose its license to operate with the state of Pennsylvania. But last week, a judge overruled the state’s decision.

As many as 40 mothers and their children are housed at the facility outside Reading. The four mothers and their children cited in Casey’s letter currently face removal from the country at any moment, though lawyers for the women say the children have been granted Special Immigrant Juvenile Status (SIJS). The status, their lawyers argue, should allow them to remain in the country pending a court hearing seeking permanent legal residency.

“Three out of the four have received their employment authorization cards (see attached). They are eligible for social security cards and await only the final step in the adjudication of their legal permanent residency,” the letter reads. “However, they remain detained with their mothers at Berks, where they have been held for nearly 600 days. Multiple requests to Immigration and Customs Enforcement (ICE) to release these families have been denied, with no individualized determination as to why.”

ICE officials, who have increased enforcement in 2017 throughout the Philadelphia region, do not comment on the facility. In fact, no ICE official out of the Philadelphia field office, has spoken with name attribution in recent memory.

After a recent raid on a Chester County mushroom farm in which 12 people were arrested for alleged undocumented status, a spokesman for the field office confirmed the raid and gave a statement that he said is attributable to “ICE officials.”

“ICE’s enforcement actions are targeted and lead driven. ICE does not conduct sweeps or raids that target aliens indiscriminately,” the statement read.

The four women in the letter are identified, but an attorney for the women and children asked that news organizations only identify them by initials: W.M. and her three-year-old son D., C.M. and her four-year-old son A., M.N. and her seven-year-old son J., and J.M. and her 16-year-old son V.

The women fear for their safety, their attorneys say.

The U.S. Supreme Court last month declined to hear arguments in the women’s appeal of their removal order, setting them up for possible deportation in the near future. It remains unclear what Homeland Security officials plan to do.

If deported, the women would be sent back to homes they fled almost two years ago in fear of their lives, their lawyers have said.

The Casey letter describes their native countries in the “Northern Triangle of Central America” -- El Salvador, Guatemala and Honduras -- as “the most dangerous areas in the world.”

“(V.) was only 14 years old when he and his mother, (J.), fled El Salvador because they received death threats from the MS-13 for defying gang recruitment. (V.) and his mother only want (V.) to be able to go to church and attend school without the fear of being murdered for refusing to join the gangs. They know they will face extraordinary challenges and, very likely, violence, if they return, as (V.) has two friends who were murdered for refusing to join the gangs,” the letter reads. “Seven-year-old (J.) and his mother (M.) have been in detention for over 550 days. According to her lawyers, (M.) is a survivor of sexual harassment and assault from gang leaders, and fled El Salvador with (J.) following threats to harm her and kidnap her son. Each of these families has a story similar to (V.), (J.), and their mothers. They fled one of the most dangerous areas in the world to seek refuge.”

Others in Congress to co-sign Casey’s letter include Sens. Bob Menendez, Cory Booker, Sherrod Brown, Kirsten Gillibrand, Mazie Hirono, Ed Markey, Elizabeth Warren and Sanders; and U.S. Reps. Lucille Roybal Allard, Nanette Diaz Barragan, John Conyers, Danny Davis, Keith Ellison, Luis Gutierrez, Pamila Jayapal, Barbara Lee, Zoe Lofgren, James McGovern, Holmes Norton, Norma Torres and Juan Vargas.