The FBI warned law enforcement agencies last month of the possibility that Tehran might try to retaliate for any US strikes on Iran by launching surprise drone attacks in California, according to a security bulletin seen by Reuters.

The confidential alert, issued by the FBI through the multi-agency Los Angeles Joint Regional Intelligence Center, surfaced publicly on Wednesday as the war that began on February 28 with massive US and Israeli bombardments of Iran stretched into its 12th day.

Speaking to reporters at the White House before ABC News first broke word of the FBI security bulletin, President Donald Trump shrugged off the notion of Iran-backed attacks on the US homeland. California Governor Gavin Newsom said he was not aware of any “imminent threats” to the state.

An unclassified copy of the security bulletin obtained by Reuters was undated. But the prospective wording of the text makes clear it was issued before the outbreak of hostilities, and that the potential for Iranian revenge attacks on the US homeland was already contemplated.

It cited FBI information that as of early February Iran “allegedly aspired to conduct a surprise attack using unmanned aerial vehicles” launched from a sea vessel against targets in California “in the event that the US conducted strikes against Iran.”

“We have no additional information on the timing, method, target, or perpetrators” of any such attack, the bulletin added.