An alert issued by the Federal Bureau of Investigation has raised concerns about the possibility of an Iranian drone attack targeting the US state of California. However, officials stress that the warning is based on unverified intelligence and does not point to an imminent threat.The memo suggested that Iran could attempt to launch unmanned aerial vehicles (UAVs) from a vessel positioned off the US coast as retaliation if the United States carried out military strikes on Iran.The disclosure of the alert drew widespread attention earlier this week after reports surfaced that the FBI had warned law enforcement agencies about the possibility of a seaborne “surprise attack.”According to the memo, the scenario involved drones launched from a ship somewhere off the American coastline. Authorities later clarified that the notice was based on raw intelligence and was circulated out of caution rather than evidence of an immediate threat.The warning was first reported by ABC News on March 11. The FBI had earlier distributed the memo to members of a Joint Terrorism Task Force last month, before the latest escalation in the Middle East conflict.The United States and Israel began carrying out strikes on Iran on February 28, raising fears of possible retaliation.

The memo released by the FBI states that the agency had received intelligence suggesting Iran might consider launching a drone attack from a vessel at sea.“We recently acquired unverified information that as of early February 2026, Iran allegedly aspired to conduct a surprise attack using Unmanned Aerial Vehicles (UAVs) from an unidentified vessel off the coast of the United States homeland, specifically against unspecified targets in California, in the event the US conducted strikes against Iran. We have no additional information on the timing, method, target, or perpetrators of this alleged attack.”The document was marked “unclassified” but also labelled as “law enforcement sensitive.” It also carried a clear warning that the information was preliminary.The memo states that, “NOT FOR DISSEMINATION TO THE PUBLIC OR PRESS” and that “THIS MESSAGE CONTATINS [sic] RAW INFORMATON [sic] SUBJECT TO REVISION AND IS PROVIDED FOR YOUR SITUATIONAL AWARENESS ONLY.”Officials familiar with the warning have repeatedly said that the information remains unverified.A California-based federal law enforcement official told CBS News that the warning was “not actionable.” Another official said, “This is unverified. There has been no information given on the timing, source, method or target of any such attack… since then, we have seen no further indications of this.”

Authorities in California have also sought to reassure the public that there is currently no confirmed threat.Governor Gavin Newsom said in a post on the social media platform X that officials are monitoring the situation closely.“While we are not aware of any imminent threats at this time, we remain prepared for any emergency in our state,” he said.The memo itself appears to have been triggered by an intelligence tip that surfaced even before the latest escalation between the United States and Iran.Despite the lack of credible details, the warning has drawn attention to a growing concern among security experts: the increasing use of long-range attack drones.

Why drone attacks are seen as a plausible threat

Even though the FBI alert may not point to a credible attack plan, experts say the scenario described in the memo is technically feasible.Long-range one-way attack drones — often called “kamikaze drones” — have become a major feature of modern warfare.These systems are designed to fly long distances before crashing into a target and detonating their payload.Such drones can travel hundreds or even thousands of miles and are relatively inexpensive compared with traditional cruise missiles. Their affordability and ease of use have made them increasingly popular among both state militaries and non-state actors.Israel has long been a pioneer in drone technology. However, Iran and its regional allies have also emerged as major developers and users of such systems.Iranian drone designs have been widely used in recent conflicts and have become particularly prominent in the war between Russia and Ukraine.

One of the most widely known Iranian drones is the Shahed-136, a long-range loitering munition that has been heavily used in recent conflicts.The Shahed-136 is a one-way attack drone designed to fly long distances before striking its target. Its relatively low cost allows operators to launch multiple drones in waves, overwhelming air defence systems.Variations of the Shahed-136 have been widely used by Russian forces in Ukraine and have also influenced the development of similar systems elsewhere.The United States has also developed comparable systems, including the Low‑Cost Uncrewed Combat Attack System (LUCAS), which was reverse-engineered from the Iranian drone design.These drones are capable of travelling long distances at relatively low altitudes, making them harder for radar systems to detect.Launching drones from shipsAnother factor that has raised concern among military planners is the flexibility of these drones.Unlike traditional missiles that require specialized launch platforms, many kamikaze drones can be launched from a variety of locations — including trucks, temporary launch racks, and even ships.Iran and the United States have both demonstrated that Shahed-type drones can be launched from vessels at sea.Importantly, such launches do not require large warships. Even smaller commercial vessels could theoretically deploy these drones.This makes it easier to conceal the drones and their launch systems before an attack.Once airborne, the drones typically fly low and slow, often below the radar horizon, making them difficult to detect early.Their relatively small size also reduces their radar, infrared, and acoustic signatures, complicating efforts to track and intercept them.

Long-standing concerns about offshore attacks

For years, the US military has warned about the possibility of attacks launched from ships positioned offshore.These attacks could involve cruise missiles or drones launched from cargo vessels or other civilian ships.Several countries, including Russia, China, Iran and the United States, have developed missile launch systems that can be hidden inside standard shipping containers.This means that a seemingly ordinary commercial vessel could theoretically carry launch systems capable of striking land targets.The threat has influenced several US military programs designed to defend the homeland.For instance, the US Air Force upgraded radar systems on its F-15C Eagle fighters to better detect cruise missiles and drones approaching from the ocean.More recently, F-35A Lightning II jets and upgraded F-16 Viper aircraft have also been tasked with homeland defence missions.These upgrades were partly driven by growing concerns about drones and cruise missiles.US military admits it is playing catch-upDespite growing awareness of the threat, US officials have acknowledged that counter-drone defenses are still evolving.“We’re behind. I’ll just be candid. I think we know we’re behind,” said Charles Costanza, commander of the US Army’s V Corps, during a panel discussion last year.“We’ve been talking about counter-UAS capability for the better part of a decade… and saw the beginning of the drone capabilities,” he said.“We aren’t moving fast enough.”Officials say the war in Ukraine has highlighted how quickly drone technology is evolving and how widely it is being adopted.

Past incidents highlight the risks

Security agencies have also investigated several mysterious drone incidents near US territory in recent years.In 2019, US authorities examined whether a Hong Kong-flagged cargo ship called the M/V Bass Strait might have been linked to drone swarms that harassed US Navy ships off the coast of Southern California.The source of those drones has never been conclusively identified.In another incident in 2024, US Representative Jeff Van Drew claimed that an Iranian “mothership” was launching drones near the US coast. The US military later rejected that claim, and Van Drew withdrew his remarks.

A warning, but not a confirmed threat

While the FBI memo has sparked debate, officials emphasize that the information remains unverified and does not indicate any immediate danger.Still, experts say the warning serves as a reminder of the growing role drones could play in future conflicts.Even if this specific intelligence tip turns out to be inaccurate, the possibility of drone attacks launched from offshore platforms remains a real concern for US security agencies.As drone technology becomes cheaper, more capable, and widely available, the challenge of defending against such threats is expected to become increasingly complex.Can Iran launch a ‘surprise attack’ on California?An alert issued by the Federal Bureau of Investigation has raised concerns about the possibility of an Iranian drone attack targeting the US state of California. However, officials stress that the warning is based on unverified intelligence and does not point to an imminent threat.The memo suggested that Iran could attempt to launch unmanned aerial vehicles (UAVs) from a vessel positioned off the US coast as retaliation if the United States carried out military strikes on Iran.The disclosure of the alert drew widespread attention earlier this week after reports surfaced that the FBI had warned law enforcement agencies about the possibility of a seaborne “surprise attack.”According to the memo, the scenario involved drones launched from a ship somewhere off the American coastline. Authorities later clarified that the notice was based on raw intelligence and was circulated out of caution rather than evidence of an immediate threat.The warning was first reported by ABC News on March 11. The FBI had earlier distributed the memo to members of a Joint Terrorism Task Force last month, before the latest escalation in the Middle East conflict.The United States and Israel began carrying out strikes on Iran on February 28, raising fears of possible retaliation.