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 ramped up its efforts to monitor potential threats to the U.S. from Iran following President Donald Trump’s decision to attack the country’s nuclear facilities, two people briefed on the matter told Reuters on Tuesday.

In the past, following other U.S. military actions, it has taken years for the full dimensions of Iran’s intended campaigns of revenge to come into view.