Two U.S. soldiers killed in training exercise

FORT HOOD, Texas (CNN) -- Two soldiers were killed early Monday during a live-fire exercise at Fort Hood, Texas, when the tank they were in burst into flames, U.S. Army officials said.

Nine other soldiers were slightly injured, mostly from smoke inhalation. The names of the victims have not yet been released.

The soldiers were part of the 4th Infantry Division, which is based at the huge central Texas facility south of Waco.

It was not yet known what caused the fire to erupt in the tank during the exercise, which happened shortly after midnight on a gunnery range on the east side of the base.

An investigating team from Fort Rucker, Alabama, is being brought in to investigate, officials said.