The political arm of a controversial company that wants to continue operating private prisons for the federal government has dramatically increased its donations to Senate candidates.

Those donations from the political action committee for the GEO Group, one of the nation’s largest private prison companies, have expanded sixfold this campaign season, compared to the 2012 cycle, from $22,000 to around $136,000. That’s based on a Roll Call analysis of the most recently available campaign contribution data from the Center for Responsive Politics.

Many of the recipients support initiatives that are important to the for-profit prison industry, such as an immigration overhaul. While the Justice Department has announced that it is phasing out the use of private prisons, the Department of Homeland Security and Immigration and Customs Enforcement continue to use such facilities.

Among those recipients are three members of the “Gang of Eight,” who in 2013 worked on comprehensive immigration legislation.

Sen. Marco Rubio is one of the biggest recipients of GEO cash. The Florida Republican has received $78,400 from individual GEO employees and from its political action committee, GEO Group PAC, since 2010.