Pennsylvania authorities expect to bring charges against most of the 30 or so Baruch College students who were on a rural fraternity retreat in December when a freshman died after a pledging ritual, a police official said this week.

Chief Harry W. Lewis of the Pocono Mountain Regional Police Department, who oversaw the investigation, said the charges would probably include homicide, which Pennsylvania law defines as anything from involuntary manslaughter, a first-degree misdemeanor that could result in less than a year of jail, to premeditated murder. He said the students could also be charged with hazing, a misdemeanor.

Charges had been expected to be filed by May, but Chief Lewis said prosecutors were still awaiting a medical report and a digital animation that would depict the events surrounding the death of the freshman, Chun Hsien Deng. Local authorities have said that Mr. Deng, 19, died on Dec. 9 after a ritual in which fraternity pledges were strapped into weighted backpacks and blindfolded, then made to find their way across a frozen lawn while others tried to tackle them.

The students were from Pi Delta Psi at Baruch, in Manhattan, and had rented a home in Tunkhannock Township, Pa.