The 9/11 Commission highlighted the urgent need for federal agencies and law enforcement officials at all levels to share information. So when top government employees hide data-sharing failures from federal investigators, it’s not always mere bureaucratic bumbling: There may be serious breaches of national security. As hard to believe as it may be in the post-Sept. 11 era, one federal agency continues to a lousy job sharing information — and it’s in the heart of the U.S. Department of Homeland Security (DHS).

Examiner readers won’t be surprised that the agency is the U.S. Citizenship and Immigration Services (USCIS), whose many flaws were exposed here last year in an editorial series called “Leaving the front door wide open.” An investigation by the DHS Inspector-General found that USCIS admitted 45,000 high-risk individuals from terrorism-sponsoring countries since 2001 largely because the agency doesn’t share critical information where it is needed within its ranks. An October 2006 General Accountability Office report noted that USCIS even granted U.S. citizenship to a suspected terrorist in 2002 without checking a critical background file that supposedly was lost. Now, no one knows for sure how many more suspected or potential terrorists USCIS has admitted for similar reasons. All current applications should be put on hold until these problems are fixed.