An annual pillow fight by freshmen cadets at the U.S. Military Academy turned bloody this year when cadets swung pillowcases packed with hard objects, injuring 30 cadets, including 24 who suffered concussions. 

Photos and video have circulated on social media showing the Aug. 20 brawl, which The New York Times reports West Point did not confirm until Thursday.

Lt. Col. Christopher Kasker told the newspaper the annual fight is organized by first-year students as a way to build camaraderie after a grueling summer of training to prepare them for plebe life.

He said upperclassmen overseeing the fight required cadets to wear helmets, but video shows many did not. Some cadets swung pillowcases believed to be packed with their helmets.

The Times noted one freshman posted on Twitter: "4 concussions, 1 broken leg, 2 broken arms, 1 dislocated shoulder, and several broken ribs. That’s one hell of a pillow fight. #USMA19."

Kasker said all cadets have since returned to duty. None of the participants have been punished.

"We are conducting appropriate investigations into the causes of the injuries,"Kasker told the paper. The academy does not plan to end the annual tradition, the Times reported.

The Times spoke to cadets who said one cadet suffered a broken leg and others suffered dislocated shoulders. 

One first-year cadet told the paper that an upperclassman told him, "If you don't come back with a bloody nose, you didn't try hard enough."

The Associated Press contributed to this report