Americans are being urged to remain vigilant following the U.S. bombing of nuclear sites in Iran over the weekend and a series of arrests involving Iranian nationals inside the United States.
The former Homeland Security Secretary under President Barack Obama is warning that the threat of terror sleeper cells on American soil is a major concern for law enforcement.
"The presence in this country of undocumented migrants or Iranian nationals who have links to Hezbollah, IRGC, is, in my judgment, a domestic law enforcement concern of the highest magnitude," said former DHS Secretary Jeh Johnson during an interview on "Fox & Friends," Wednesday.
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Following the strikes, the Department of Homeland Security released a memo warning of a "heightened threat environment across the United States" due to the involvement of the U.S. in the conflict between Israel and Iran. Iranian state television has also issued threats, stating that all American citizens or military personnel in the region became legitimate targets.
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Earlier this week, Immigration and Customs Enforcement (ICE) announced the arrests of over a dozen Iranian undocumented nationals living in the U.S. Some of those arrested were accused of violent crimes such as domestic assault, drug offenses, and weapons possession. One individual had also served as a sniper in the Iranian army as recently as four years ago.
Johnson believes the threat may be larger than the recent arrests suggest and that more migrants may be seized in connection to Iran.
"That's not necessarily all of them," he said. "My educated speculation is that law enforcement has been tracking these individuals for a while in this country to follow leads, to see who they are in contact with."
Other officials have voiced similar concerns, with many linking the increased threat of sleeper cells to the Biden administration's more lenient border policies. Border czar Tom Homan told FOX Business that nearly 2,000 migrants slipped past law enforcement daily under the previous White House.
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"We don't know who they are, where they came from, why they're here, but they got away," said Homan on Tuesday, going on to call it the "biggest national security vulnerability" the country has seen.
Besides Iranian attacks, Johnson noted that those with extremist ties could act independently in response to the growing tensions in the Middle East.
"Sleepers don't necessarily follow the direction from their sponsors," he said. "Somebody who's here in the United States who has links to the IRGC, to Hezbollah, may decide to take matters into their own hands."
The FBI has shifted some of its resources to boost cybersecurity and expand counterterrorism initiatives in response to the threat. Johnson emphasized that Americans should not panic and continue to live their lives as normal.
Instead, he urged the public to remain vigilant and report any suspicious activity to the authorities.
"'If you see something, say something' is still a valid public safety tool," he said. "It does make a difference."
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