U.S. President Barack Obama on Saturday called for a thorough investigation of the Nov. 5 mass shooting at Fort Hood, Texas.

Speaking in his weekly radio and Internet address released by the White House, the president said that he hopes that investigators would conduct a careful review of the shooting, which left 13 dead and 29 wounded.

Obama said, "given the potential warning signs that may have been known prior to these shootings, we must uncover what steps - if any - could have been taken to avert this tragedy."

He was referring to new discoveries that Nidal M. Hasan, the lone suspect in the shooting, had tried to communicate with someone overseas whom U.S. authorities were monitoring.

Separately, officials said there is new evidence that Hasan, a 39-year-old licensed U.S. Army psychiatrist who worked at a hospital in Fort Hood, had been in contact with someone on a U.S. "kill or capture" list of al-Qaida and Taliban targets.

Members of Congress have also called for investigations into whether government intelligence agencies failed to recognize clues that Hasan "had fallen under the thrall of extremist ideology".