The threat of sleeper cells in the U.S. has “never been higher," though there are no current specific threats, according to U.S. Customs and Border Protection (CBP).

A memo sent Saturday from CBP Commissioner Rodney Scott, obtained by The Hill’s sister network NewsNation, said "thousands of Iranian nationals have been documented entering the United States illegally and countless more were likely in the known and unknown got-a-ways."

“Though we have not received any........

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