The Secret Service said it is "aware" of a photo that appeared to show an image of an ISIS flag in front of the White House.
If authentic, the photo showed a hand holding up an image of a flag for ISIS (also known as ISIL or Islamic State), displayed on a smartphone, on Pennsylvania Avenue in front of the White House fence. That area, closed off to street traffic, is frequented by thousands of tourists every day.
It was tweeted from an apparently pro-ISIS Twitter handle @sunna_rev on Aug. 9.
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"We have an intelligence division whose mission is to assess information that we receive every day for dangerousness or potential threat level," Secret Service spokesman Ed Donovan told ABC News. "We are aware of the image and will take the necessary and appropriate follow up steps."
The Secret Service did not respond to an additional question about whether the tweet was believed to be authentic. The FBI has not yet responded to ABC News' request for comment on the tweet, its suspected origin, or whether it signifies a serious threat to the U.S.
A senior U.S. intelligence official told ABC that use of Twitter is consistent with ISIS practices. The group has shown to be at the forefront of social-media use among terrorist and militant groups, the official said.
Another photo displayed a note handwritten in Arabic. It read, "Soldiers of the Islamic State of Iraq and Syria will pass from here soon," followed by a Koran verse that read, "and Allah is perfecting His Light even though the disbelievers hate (that)."
In the image, the note was dated June 20, 2014. It was unclear where the photo was taken, but two American flags appeared over an arched entryway.
"We are in your state / We are in your cities / We are in your streets," the tweets read.
On Aug. 7, President Obama announced that the U.S. military would conducting airstrikes against ISIS targets in northern Iraq, where the group has seized territory and is battling Kurdish forces not far from Erbil, where the U.S. military has set up a joint operations command center. ISIS has swiftly risen to control large swaths of Iraq and Syria after seizing weapons and reportedly selling oil to finance its war against Bashar al-Assad's Syrian regime.
ISIS has issued threats against the U.S. homeland before. In a recent video series, Vice Media embedded with ISIS militants, and an ISIS militant told a Vice camera, "God willing, we will raise the flag of Allah in the White House."
ABC News' Faisal Alkadiri contributed to this report.