U.S. officials have issued a warning to law enforcement agencies after intercepting an encrypted transmission believed to be linked to Iran’s government, raising concerns it could signal the activation of covert operatives or “sleeper cells.”

According to an internal bulletin first reviewed by ABC News, the message was sent through a broadcast system operating outside normal internet and cellular networks and required a special encryption key to access. The alert said the communication may have been directed at “clandestine recipients” across several countries.

Authorities say the broadcast appeared shortly after Ali Khamenei was reportedly killed in a U.S.-Israeli airstrike on Feb. 28, a development that has sharply escalated tensions between Iran and Western allies.

Officials emphasized that the contents of the encrypted message remain unknown, and there is currently no confirmed threat tied to a specific location. However, the sudden appearance of a new encrypted broadcast station with international reach prompted federal agencies to urge heightened vigilance.

Law enforcement agencies have been advised to monitor unusual radio activity and report suspicious communications that could indicate coordination between covert operatives.

Earlier warning about potential drone attack

The alert follows a previous notice sent by the Federal Bureau of Investigation warning that Iran could attempt a retaliatory drone attack against targets on the U.S. West Coast if the United States launched military strikes against Iran.

That notice said Iran allegedly considered deploying unmanned aerial vehicles from a vessel off the U.S. coast, though investigators acknowledged they had no details about timing, targets, or operational plans.

Concerns about sleeper cells

Iran and its allied networks have long been accused by Western intelligence agencies of maintaining sleeper cells around the world—operatives who live quietly for years before being activated to carry out attacks.

The possibility of such activity has drawn concern from U.S. lawmakers. Ted Cruz, a Republican senator from Texas, said the current security environment raises the risk of terrorist incidents.

“The risk of terrorism right now is quite high,” Cruz said while speaking on Capitol Hill.

Recent attacks in the United States—including a mass shooting in Austin and an attempted bombing in Manhattan—are under investigation for potential extremist connections. Authorities have linked some suspects in separate incidents to the terrorist organization Islamic State.

Incidents targeting Western sites

Security concerns are not limited to the United States. Authorities in several countries are investigating attacks against Western or Jewish institutions:

• Gunfire was reported at the United States Consulate General Toronto, though no injuries occurred.

• An explosive device detonated near the Embassy of the United States, Oslo, with investigators considering terrorism as a possible motive.

• Synagogues in Toronto were targeted by gunfire, and a bomb exploded near a synagogue in the Belgian city of Liège.

Officials in Europe and North America say investigations are ongoing and it remains unclear whether these incidents are directly connected to Iran or the broader geopolitical conflict.

For now, U.S. authorities stress that the encrypted transmission has not been definitively linked to any specific attack, but its appearance is significant enough to warrant increased monitoring and preparedness by law enforcement agencies.