Army spokesman: 'We are aggressively following every possible lead'
A US Army major suspected of shooting colleagues at the Fort Hood military base in Texas last week will face 13 initial murder charges.
Maj Nidal Malik Hasan, 39, was shot by police and remains in hospital. He has refused to speak to investigators.
President Obama has ordered a review after US intelligence authorities said they knew Maj Hasan had been in contact with a cleric sympathetic to al-Qaeda.
Maj Hasan was said to be unhappy about a possible deployment to Afghanistan.
The shootings took place at Fort Hood's crowded Soldiers Readiness Processing Center, where troops get medical check-ups before deploying abroad.
HASAN TRIAL PROCESS
Trial by court martial
Jury comprising military personnel
Verdict decided by secret ballot - two-thirds majority needed
Unanimous vote required for death penalty
At least 29 people were hurt in the attack.
Major Nidal Hasan has been under armed guard in a hospital since being wounded in the shooting.
"Today I've confirmed that US Army Major Nadal Malik Hasan, a 39-year-old psychiatrist assigned to Darnell Medical Centre here at Fort Hood, has been charged with 13 specifications of pre-meditated murder under Article 118 of the Uniform Code of Military Justice," Chris Grey, a spokesman for the army's criminal investigation division, told a news conference.
"These are initial charges and additional charges may be preferred in the future, subject to the ongoing criminal investigation."
Maj Hasan has received the charges in hospital, his lawyer told the Associated Press news agency. He is reported to have been taken off a ventilator, and to have been talking to medical staff.
"I directed an immediate inventory be conducted of all intelligence in U.S. Government files that existed prior to 6 November 2009, relevant to the tragic shooting at Fort Hood, Texas, especially anything having to do with the alleged shooter, Major Nidal Malik Hasan, US Army," Mr Obama said in a statement.
"Additionally, I directed an immediate review be initiated to determine how any such intelligence was handled, shared, and acted upon within individual departments and agencies and what intelligence was shared with others.
"This inventory and review shall be conducted in a manner that does not interfere with the ongoing criminal investigations of the Fort Hood shooting."
Amid fears of a possible anti-Muslim backlash after the attack, President Obama has stressed the multinational diversity in the US armed forces.
"They are Americans of every race, faith, and station. They are Christians and Muslims, Jews and Hindus and non-believers.
"They are descendants of immigrants and immigrants themselves. They reflect the diversity that makes this America," he said in the aftermath of the shooting.
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