The FBI is returning national security agents who were ordered to focus on immigration cases back to their old jobs due to concern about potential threats from Iran

The directive related to counter-terrorism, counterintelligence and cyber security agents who work on issues connected to Iran. FBI field offices in Chicago, Los Angeles, San Francisco, New York and Philadelphia have canceled rotations for agents to work on immigration issues, one of the sources said.

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.