 -- The U.S. Military Academy at West Point is investigating an annual pillow fight at the school that turned bloody and left 30 cadets injured, most of them with concussions.

The school’s superintendent says appropriate action will be taken once an investigation by military police is concluded.

The pillow fight is an annual tradition stretching back more than a century and is intended to build class spirit among incoming first year students known as plebes. Held in the school’s main courtyard it comes at the end of a summer training period before the plebes enter the academic year.

The pillow fight held on August 20 resulted in 24 cadets suffering concussions and others suffering injuries including a broken nose, a dislocated shoulder and a broken cheekbone. The New York Times first reported the violence at this year’s fight. Sources told the Times that some cadets had placed helmets inside the pillowcases used in the fight.

Video posted on social media shows hundreds of cadets pouring into the courtyard striking each other with pillows for an extended period of time.

In a statement, the school's superintendent Lt. Gen. Robert L. Caslen Jr. said spirit events like the pillow fight are held "in order to build esprit de corps among their class, especially following their tough first summer."

"While these spirit events do occur, we never condone any activity that results in intentional harm to a teammate. Although the vast majority of the class appears to have maintained the spirit of the event; it is apparent that a few did not," Caslen said.

"A military police investigation that began the night of the incident is ongoing," he said. "I assure you that the chain of command will take appropriate action when the investigation is complete."

Caslen said that 30 cadets were evaluated by medical personnel.

"Specifically, 24 cadets were diagnosed with concussions, none of them severe," he said. "Other injuries sustained included a broken nose, a dislocated shoulder, and a hairline fracture of a cheekbone for one of the concussed cadets."

He said that four other cadets were also evaluated by medicate personnel and were released with no injuries.

"No cadets left the Academy because of their injuries," Caslen said. "All cadets have been returned to duty."

Medical personnel will follow up with the injured cadets "including following established evidence-based concussion care protocols. 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."

"I take full responsibility for all actions that occur here at West Point to include the event on August 20, 2015," Caslen said. "We remain committed to the development of leaders of character. We will continue our investigation, ensure accountability, and reinforce with the Corps that we must all take care of our teammates."