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A pillow fight at the United States Military Academy at West Point turned so violent that it caused concussions in 24 cadets, the superintendent of the school told NBC News on Saturday.

The Aug. 20 pillow fight — an annual tradition at the prestigious academy and a way for first-year cadets to have some fun after a rigorous month of summer training — also resulted in other serious injuries: a broken nose, a dislocated shoulder, and a hairline cheekbone fracture, school officials said.

In total, 30 cadets were evaluated by medical personnel, Lt. Gen. Robert L. Caslen Jr. said in a statement. Four were released with no injuries, and no cadets left the academy due to their injuries.

The raucous fight was first reported by The New York Times, which said one cadet ended up with a broken leg and another was knocked unconscious and didn't return to school. Caslen's statement contradicted that, adding, "All cadets have been returned to duty."

According to the Times, the class spirit-building activity turned bloody when cadets at the taxpayer-funded academy put hard objects — believed to be helmets — in their pillowcases.

"Although the vast majority of the class appears to have maintained the spirit of the event; it is apparent that a few did not. A military police investigation that began the night of the incident is ongoing. I assure you that the chain of command will take appropriate action when the investigation is complete," Caslen said.

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Medical personnel have done comprehensive follow-ups with injured cadets, he said.

"In addition, the chain of command and medical professionals will continue follow-up with these cadets to address any negative impact on their performance or experience as a cadet," he said.

A spokesman for the academy, Lt. Col. Christopher Kasker, told The Times that the pillow fight is organized by first-years and is overseen by upperclassmen who take "mitigating measures" to keep everyone safe, including requiring participants to wear helmets.

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He added that no one has been punished and there are no plans to put an end to the yearly ritual, which The Times said dates back to at least 1897.

Most intense pillow fight of my life! Plebe Pillow Fight 2015, one crazy tradition here. #USMA19 pic.twitter.com/am1x3MCPkX — Nicholas Alonso (@nnniiico) August 21, 2015

Ret. Col. Jack Jacobs, a military analyst for NBC News who teaches at West Point, said in his 40 years of being associated with the academy, he had never heard of cadets swinging pillowcases that contained hard objects.

"Punishment could be dismissal from the academy, or they could be eliminated and permitted back a year later, which happens from time to time," Jacobs told NBC News. "If they do not dismiss anyone, punishment would include restricted movement, free time, and march punishment tours.”

Ultimately, Jacobs said, the responsibility falls on people higher up in the chain of command for keeping cadets safe.

"If something like this happens, it’s because you didn't follow procedure. You are responsible for the health, safety, and care for the people under you," he said. "The cadets I talked to about it all say the same thing. Someone didn’t do what they were supposed to.”

Caslen said he took "full responsibility" for all actions at West Point, including the pillow fight.

"We will continue our investigation, ensure accountability, and reinforce with the Corps that we must all take care of our teammates."