The Immigration and Customs Enforcement (ICE) agency’s new plan to utilize private prisons in its efforts to expand detention facilities for illegal aliens is facing push-back from the American Civil Liberties Union (ACLU).

According to data from ICE, the agency arrested 28,011 illegal aliens from Jan. 22 to Sep. 9, a reported 179 percent increase over the same period of time during the last year of the Obama administration.

ICE currently houses between 31,000 and 41,000 immigrants per day in public and privately-owned prison facilities. The White House has requested a provision of $1.2 billion in the 2018 federal budget to expand ICE’s capacity to house up to 48,000 immigrants per day.

To that end, USA Today is reporting ICE recently sent out requests to Chicago, Detroit, Salt Lake City and St. Paul, Minn., to identify privately-run prison sites that it could use to detain more immigrants, although the agency has not yet announced its plans publicly.

In a Thursday statement, the ACLU said it was joining 13 legal service providers and immigrant rights organizations in opposing the move.

“This attempt to expand ICE jails is part of the continued assault on immigrant communities, and a boon to the private prison industry,” said the ACLU’s director of immigration policy, Lorella Praeli.

The ACLU said it fears that immigrants sent to the facilities would be without legal counsel or other aid in “a detention system notoriously lacking in transparency and accountability.”

“ICE’s intention to expand detention in areas surrounding four of the nation’s largest cities is an attack on the freedom of long-term residents, including Dreamers, and asylum seekers fleeing persecution in their home countries,” Praeli said in a statement.

Democrats have warned that an increase in capacity for detainment of illegal aliens, as well as President Trump’s proposed border wall, is a red line that won’t be crossed, even as they push to reach a deal with Republicans regarding protections for so-called Dreamers who were brought to the U.S. illegally as children.