The FBI says that a US Army major suspected of killing 13 people was not part of a "broader terrorist plot".
The BBC reports the bureau noticed Major Nidal Hasan in December as part of an unrelated inquiry by the Joint Terrorism Task Force, but did not raise concerns.
Investigators say his communications with another person were in line with his job as an army psychiatrist.
Major Hasan remains in hospital but has regained consciousness after being shot by police during the attack last Thursday.
Thirteen people died and another 29 were injured in the shooting at Fort Hood base in Texas.