Five men face charges of felony hazing; police say those men were most involved in the planning of the event. The 17 others face misdemeanor hazing charges.
Of the 13 men to surrender so far, seven did so in DeKalb. Leverton said those seven posted bond and were released. He said he didn't know if the others, who turned themselves in to police in other communities, also had posted bond.
In a statement Monday, Bogenberger's family called on college administrators and fraternity officials to help put an end to hazing and other "initiation rituals."
NIU said 31 students are accused of violating the school's code of conduct. Those students could face penalties ranging from reprimand to expulsion.
University officials also said they work with fraternities and sororities to educate members about the risks of drinking, blood alcohol content, responsible drinking, signs of intoxication and alcohol poisoning. Training is held at the start of the academic year for members of the Greek community, and more than half of an organization's members must participate in a training session in order to hold a social event that includes alcohol.
NIU policy requires fraternities and sororities to register social events and get university approval. The university said Pi Kappa Alpha leaders did not officially register the Nov. 1 event with NIU or the fraternity's national chapter.
The international fraternity suspended the local chapter and said it would cooperate in the investigation. In a statement from its Memphis, Tenn., headquarters, the fraternity said it has "strict standards with respect to alcohol and hazing."