Officials across the US are on heightened alert after the US bombing of nuclear facilities in Iran.
There is no specific threat but in recent days, the FBI and Department of Homeland Security (DHS) have spoken with governors and law enforcement agencies across the country about the heightened threat environment.
The FBI has also shifted some of its agents, who have been helping on immigration-related cases, back to counter-terrorism efforts, sources told the BBC's US partner CBS.
Within two days of the Iranian strikes, US immigration officials arrested 11 Iranian citizens in the US, including men with alleged ties to Iran's military and paramilitary proxy groups.
