The infrastructure and personnel tied to Iran’s past nuclear weapons work continue to operate under the radar, according to senior Trump administration officials, who announced sanctions on a host of individuals and organizations that have worked to keep critical infrastructure of Iran’s nuclear weapons program in place.

The State Department on Friday announced sweeping new sanctions against “a key Iranian nuclear organization” for its participation in schemes to circumvent U.S. sanctions in a bid to obtain “weapons of mass destruction (WMD) and WMD delivery systems.”

The sanctions are part of the Trump administration’s push to strangle Iran’s economy as well as a secret nuclear procurement network that has enabled Tehran to continue its most sensitive nuclear work despite international prohibitions on such activity.