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(CNN) —  

The family of deceased Cornell University student Antonio Tsialas is offering a $10,000 reward for any information on how and why their son died last month.

The Tsialas family is taking out a full-page ad in The Cornell Daily Sun, the university’s student daily newspaper, on Monday and Tuesday asking the student body for help, family attorney David Bianchi told CNN in an interview on Sunday.

Tsialas, an 18-year-old freshman from Miami, was last seen on October 24 – the same day he and other first-year students attended “an unregistered fraternity-sponsored event” where alcohol was served, university President Martha E. Pollack wrote in a statement posted on the school’s website.

Tsialas was reported missing the next day, university’s Vice President for Student and Campus Life Ryan Lombardi said in another message to students. His body was recovered on October 26 inside the Fall Creek Gorge, which is part of the university’s botanic gardens, after an extensive search, Lombardi said.

No foul play was suspected, Lombardi said. An autopsy is pending, Bianchi said.

Authorities, including Cornell University Police, are investigating, Lombardi and Police Chief Dave Honan said in a joint statement earlier this month.

Honan said authorities have received more than 150 leads. Several subpoenas have been issued, Honan said.

In her statement, President Pollack wrote, “While we do not yet have definitive answers about the cause of his death, it is already widely known that an unregistered fraternity-sponsored event took place on October 24, that alcohol was served, and that first-year students, including Mr. Tsialas, were in attendance.”

Pollack said the events “regrettably follow a pattern of misconduct in the Greek-letter system.” She said over the past two years, “numerous fraternities have been found to have engaged in misconduct over that time sufficient to merit suspension of their recognition by the university.”

In an email Sunday night, Cornell Interfraternity Council President Cristian Gonzalez referred questions to Cornell University Police.

Days after Tsialas’ body was recovered, Cornell’s fraternities “overwhelmingly” decided to suspend all registered social events planned for the weekend after Halloween, The Cornell Daily Sun reported. Gonzalez told the paper the decision was prompted by Tsialas’ death.

“We believe that it would be disrespectful and wrong to be celebrating this weekend given the passing of Antonio,” Gonzalez said in a message to paper then.

Later, the university’s IFC banned nearly all social events for the fall semester, with exceptions such as events at a chapter’s house with licensed bartenders and security, The Daily Sun reported.

“We have an obligation to protect the safety of both our members, our guests, and the larger Cornell community and we believe that taking this action allows us to draw back and reassess our shortcomings and enact substantial change,” said the ban, which was cosigned by more than two dozen fraternity presidents.

Bianchi said the last time Tsialas’ mother saw him was when they had dinner on the evening of October 24 at an off-campus restaurant. Tsialas’ mother was visiting the campus for the university’s “Parents Weekend” and his father was due to arrive the following day.

“What started as a beautiful weekend with our son Antonio turned into our worst nightmare,” his mother, Flavia Tsialas said in a recent Facebook post.

She recalled “he was so cheerful” when they met for dinner.

“We spoke of how happy he was at Cornell and all of his exciting future plans,” she said. Tsialas was a student in the College of Arts and Sciences, the university said.

Bianchi said the Tsialas family is “very upset that this fraternity would host a party in violation of the rules.” He alleged the fraternity served alcohol to underage first-year students.

“Antonio got drunk, left the event and then he disappeared and we don’t know exactly how he died,” Bianchi said. “We’re hoping … that people will come forward with information from that night.”

CNN’s Monica Haider and Darran Simon contributed to this report.