The FBI is investigating a fake tweet from an Associated Press account that claimed that two explosions had occurred at the White House and injured President Obama. The AP suspended its account on Tuesday afternoon after hackers gained access.
The bogus tweet briefly set off a firestorm of confusion on the microblogging service.
"Earlier this afternoon the @AP Twitter account was hacked. Out of a sense of caution, we have suspended other AP Twitter feeds," said Paul Colford, director of AP media relations, in a statement. "We are working with Twitter to sort this out.”
A spokesman for the Secret Service said Tuesday that the agency was aware of the Twitter hack, and would be monitoring the situation and take any appropriate steps to follow up.
In its own report, the AP said the hacker attack on its Twitter account and mobile Twitter account were preceded by phishing attempts on the wire service's corporate network.
For phishing attacks, hackers send people malware-laced messages that appear to be from people they know in an attempt to compromise their computer and get access to their passwords and other information.
White House Press Secretary Jay Carney confirmed that the president is "fine" during the daily press briefing with the White House press corps.
At the top of the briefing, AP reporter Julie Pace — who traditionally asks the first question of press secretary Jay Carney — noted that the wire service's Twitter feed had been hacked and was posting "obviously false" reports.
White House press secretary Jay Carney thanked her for the clarification.
"I appreciate that," Carney told Pace. "And I can say that the president is fine, I was just with him."
The false tweet also sent the Dow Jones Industrial Average plunging after it was posted, but it quickly recovered after Carney confirmed that the report was erroneous.
The Syrian Electronic Army, or SEA, claimed responsibility for the hacker attack on the AP.
"This small tweet created some chaos in the United States in addition to a decline in some U.S. stocks," SEA said on its website.
The group says its cause is to support the Syrian government and President Bashar Assad, as well as "spread the truth about all those who wish ill of our country."
It has claimed responsibility for recent hacker attacks on the "60 Minutes" Twitter account and NPR's website and social media accounts.
—This report was originally published at 2:06 p.m. and last updated at 6:08 p.m.