(Adds White House statement, background on previous shootings)
By Jon Herskovitz
AUSTIN, Texas, April 2 (Reuters) - At least one gunman opened fire at Fort Hood on Wednesday, injuring an unknown number of people at the U.S. Army base in central Texas that was the scene of a shooting rampage in 2009, officials said.
"There has been a shooting at Fort Hood and injuries are reported. Emergency crews are on the scene. No further details are known at this time," the base said in a statement.
Local news reports said there may be two suspected shooters, while CNN reported that one shooter was believed to be dead, citing a U.S. official.
The number of shooters or casualties could not be confirmed by Reuters.
NBC reported that 8 people were wounded in the shooting, 4 of them critically.
News of the shooting, the third such incident at a military base in the United States in about six months, was being relayed to President Barack Obama, the White House said.
"The president has been informed of reports of a shooting at Fort Hood. He'll continue to receive updates on the situation throughout the evening," principal deputy press secretary Josh Earnest told reporters.
The base has been put on lockdown and police were securing its perimeter, police and military officials said. Helicopters could be seen circling the base in live TV footage broadcast from the scene.
Authorities advised those on the post to stay away from windows and to keep doors closed and locked.
Central Texas College, which has a Fort Hood campus, ordered an immediate evacuation of all students and staff, and canceled all classes.
In 2009, a former Army psychiatrist shot dead 13 people and wounded 32 others in a shooting spree at Fort Hood.
In September, a gunman opened fire at the Washington Navy Yard, killing 12 and wounding 4 before being slain by police. Last month, a civilian shot dead a sailor aboard a ship at a U.S. Navy base in Norfolk, Virginia. (Additional reporting by Lisa Maria Garza in Dallas and Caren Bohan in Washington, editing by G Crosse)