A senator called upon the new director of Homeland Security to stop prolonged, indefinite detentions of immigration detainees awaiting hearings.

Sen. Richard Blumenthal (D-Conn.) said Immigration and Customs Enforcement is holding tens of thousands detainees “at a cost to taxpayers of about $2 billion each year… for the limited purpose of ensuring they appear at their hearings and comply with final decisions in their immigration cases.”

“Many individuals are subjected to prolonged detention even though they have substantial challenges to their removal,” Blumenthal wrote to Homeland Security Secretary Jeh Johnson, protesting that under federal law they can be released “contingent on a finding that they pose no significant danger to public safety or flight risk.”

“Unnecessary detention continues to cause harm to individuals and their families and impose a significant financial burden for taxpayers, ” the letter continues.

Blumenthal urges two “administrative actions” from the DHS “to help resolve this inexcusable denial of due process rights and to roll back the unnecessary costs of physical detention.”

He requested bond hearings for all immigration detainees held for more than six months. “Notably, two-thirds of those granted bond hearings in the Central District of California were ordered released by immigration judges, suggesting that many of the costly detentions that have not been reviewed are unnecessary,” Blumenthal wrote.

The senator also requested that the DHS “adopt an interpretation of mandatory ‘custody’… that includes forms of custody short of physical detention, such as electronic monitoring or house arrest.”

“DHS should not waste resources to needlessly hold immigrants who could successfully and safely be released,” he added. “…The Supreme Court has never interpreted ‘custody’ to require physical incarceration.”

“These two administrative actions can, and should, be taken as soon as possible. I urge DHS to adopt these changes in order to rectify the indefensible denial of due process rights to ICE detainees and to reduce the unnecessary costs of physical detention.”