On Wednesday, Sens. Chuck Grassley, R-Iowa, and Richard Blumenthal, D-Conn., sent a letter to U.S. Immigration and Customs Enforcement asking “what steps ICE has taken to document and justify the use of segregation.” The letter was spurred by “recent allegations of the misuse of solitary confinement” in ICE detainment centers, the senators wrote, citing an investigation by the International Consortium of Investigative Journalists, The Intercept, NBC News, and other reporting partners.

The ICIJ investigation, which involved a review of more than 8,400 reports describing placement in solitary confinement from 2012 to early 2017, found that ICE uses isolation as a go-to tool, rather than a last resort, to punish vulnerable detained immigrants. Our reporting also included interviews with Ellen Gallagher, a Department of Homeland Security whistleblower who sounded the alarm about ICE’s misuse of solitary confinement for years before going public with her concerns for the first time in interviews with the reporting consortium. Gallagher’s attempts at whistleblowing, which date back to 2014, included outreach to congressional offices. Grassley, along with then-Sen. Al Franken, D-Minn., took perhaps the most serious step in response to Gallagher’s complaints, sending a June 2015 letter to then-Secretary of Homeland Security Jeh Johnson, citing her findings about the use of solitary confinement and demanding an explanation. “I have been blowing the whistle on this issue for many years to almost complete silence. One notable exception was the willingness of Senators Grassley and Franken in 2015 to write a letter seeking accountability,” Gallagher wrote in an email on Wednesday. “Then as now, it is hard to express my gratitude that a bipartisan pair of Senators remain willing to challenge the widespread, abusive use of solitary confinement for civil detainees. I pray that DHS will treat their concerns and my disclosures with the seriousness they deserve.”

“It is hard to express my gratitude that a bipartisan pair of Senators remain willing to challenge the widespread, abusive use of solitary confinement for civil detainees.”

Grassley and Blumenthal both sit on the Judiciary Committee, which has oversight over ICE. Grassley is the first Republican on the panel to publicly respond to our investigation; though he has not called for a hearing on the issue, a reaction from him could carry more weight than demands by the panel’s Democrats, who do not have the power to independently convene a hearing in the GOP-held Senate. Blumenthal responded to our May report by calling for an investigation into ICE’s use of solitary confinement. Sen. Cory Booker, D-N.J., last month sent a letter asking Judiciary Committee Chair Lindsey Graham, R-S.C., to convene a hearing on ICE’s “egregious and appalling abuses,” including the use of solitary confinement, while Sen. Elizabeth Warren, D-Mass., demanded answers from ICE about its use of solitary confinement. In the Wednesday letter, addressed to acting ICE director Matthew Albence, Grassley and Blumenthal also cite recent investigations by the Department of Homeland Security’s Office of Inspector General, or OIG, which reveal discrepancies in ICE’s documentation of how it uses solitary confinement. “It is imperative that ICE swiftly resolve any lacking oversight or improper documentation pertaining to the use of segregation,” they wrote, using the label that ICE applies to solitary confinement, which is typically understood to mean total isolation with no human contact for at least 22 hours a day.