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Tweets linked to ISIS target hurricane cities

  • Threatening social media posts that appear to be connected to ISIS are targeting Miami, Houston and other cities.
  • CNBC obtained a "situation awareness" document from the Homeland Security Bureau.
  • At least one posting calls for attacks on the "relief centers housing displaced people" from the hurricanes and subsequent floods.
A destroyed trailer in Key Largo, Fla., after Hurricane Irma swept through the area.
Contessa Brewer | CNBC
A destroyed trailer in Key Largo, Fla., after Hurricane Irma swept through the area.

Law enforcement officials have been advised to step up alerts for "lone wolf attackers" in Miami, Houston and other cities in the wake of threatening social media posts that appear to be connected to ISIS, according to an internal government intelligence document.

The confidential "situation awareness" document, obtained by CNBC, is dated Sept. 14 from the Homeland Security Bureau's Southeast Florida Fusion Center. The center is the Miami-Dade Police Department's Homeland Security Bureau. It was sent to law enforcement and "homeland security communities."

"On Sept. 11, there was a twitter posting that appears to be authored by the Islamic State of Iraq and Syria (ISIS) that threatens Washington, New York, Los Angeles, Houston, Miami and Las Vegas, the document states.

The posting said there were "a lot of opportunities for the Soldiers of Islamic state to target, the Question is When?"

The document, which is unclassified, mentions a Newsweek article dated Sept. 6 that cites another ISIS posting calling for attacks on Houston relief centers. The article said: "To all the (lone mujahids) in the U.S. (warrior), pop down to Houston and drop in at any of the relief centers housing displaced people from the Houston floods, make sure to bring lots of supplies/gadgets/toys to see if you can help put any (unbeliever) out of their misery."

The document also states: "Another Jihadist, in Arabic writing said, 'A historic hurricane will hit Florida, especially the city of Miami soon' One that would leave an 'international tragedy' on American soil. He quotes Allah saying that a 'roaring wind in the days of the snakes' had been sent and makes use of a hurricane emoji."

An analyst comment in the document says that "these posts appear to be more aspirational than operational, with hopes that their followers would then act on calls for attacks. Incidents involving lone wolf attackers have demonstrated the potential danger, lethality and effectiveness of a rehearsed small arms or knife attack that can be carried out by a single individual with little or no training. It also underscores the potentially higher consequences of an assault attack involving multiple operatives."

The alert states, "officers should continue to maintain situational awareness of their surroundings."

States and local governments operate fusion centers for intelligence information sharing and analysis, according to the Department of Homeland Security. The document is labeled unclassified and for official use only.

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