Over a period of five and a half hours on Monday morning someone using a hijacked Fox News Twitter account posted a series of false tweets that President barack Obama had been the assassinated.

The incident is currently under investigation by the U.S. Secret Service.

According to a source close to the matter, the network informed Twitter that its account had been hijacked as soon as false tweets were discovered on Monday morning.

Administrators could not get into the account because the password had been changed and the hackers disabled the "change password" function. The sources said that Fox personnel could only wait and watch hackers use the account in the five and a half hours it took for Twitter to respond.

At that point, Twitter suspended the account and returned control to Fox personnel, who immediately deleted tweets posted by the hijackers.