Cadets cheer during the first half of an NCAA college football game between Army and Fordham University in West Point, New York on Sep 4, 2015. More than a dozen students were injured during the annual pillow fight by first year cadets on Aug 20, 2015, when some participants put hard objects inside their pillow cases, according to a story in the New York Times on Saturday. [Photo/IC]

WASHINGTON, Sept 5 - The US Army launched an investigation Saturday after an annual pillow fight by first-year cadets at the US Military Academy at West Point in New York turned bloody and injured dozens.

The pillow fight held on Aug 20 led to 24 cadets suffering from concussions and others suffering injuries including a broken nose, a dislocated shoulder and a broken cheekbone, US Army authorities said in a statement Saturday.

"...[W]e never condone any activity that results in intentional harm to a teammate," said the statement. "Although the vast majority of the class appears to have maintained the spirit of the event, it is apparent that a few did not."

While the statement said a military police investigation was underway, it did not explain why the academy kept secret the brawl till now.

Details of the violence at the century-long West Point traditional event was first reported by the New York Times on Friday, which said a group of cadets stuff pillowcases with hard objects.

Though few report of similar melee at West Point in the past could be found, the New York Times said a cadet put a lockbox in a pillowcase and injured others in 2012.

Citing a male cadet who spoke on condition of anonymity, the Times reported that an upperclassman told first-year cadets that if they did not come back with a bloody nose, they did not try hard enough.

The pillow fights date back to at least 1897, the Times reported, citing a 1901 congressional inquiry on hazing.

The 2013 fight was canceled after a cadet put a lockbox in a pillow case during the 2012 event and hurt other cadets, the paper reported.