The 7th US Circuit Court of Appeals blocked the release of hundreds of immigrants detained during a Chicago area immigration crackdown in a decision on Thursday that also allows extension of a consent decree outlining how federal immigration agents can make warrantless arrests.

The consent decree has been in the spotlight amid the Trump administration’s Chicago-area immigration crackdown that’s led to more than 4000 arrests. Last month, a judge had ordered the release of more than 600 immigrants on bond, which the appeals court paused. Around 450 remain in custody.