Police were told that Timothy Piazza fell down the basement stairs at a Pennsylvania State University fraternity house at around 11 p.m. Thursday.

But they weren’t called to the house until the next morning, at around 10:49 a.m. Friday.

Piazza was eventually taken to a medical facility and later died. Now investigators are looking into his death, working to figure out what happened in the nearly 12 hours between Piazza’s fall and the emergency call, and why so much time passed before officers were summoned.

Authorities were told that Piazza had attended a party at the Beta Theta Pi fraternity Thursday night, Lt. Keith Robb of the State College Police Department said at a news conference.

“They knew he fell at 11,” Robb told The Washington Post in a phone interview Tuesday. “They didn’t report it until 10:49 the following morning, hence why we’re investigating.”

When asked what happened to Piazza after the fall — whether he was moved somewhere, for example, or whether the party continued — Robb told The Post that it was under investigation.

“We’re not releasing any information about that at this point,” he said. “We will later. But that is still under investigation.”

An autopsy was conducted Tuesday morning, Robb said.

Piazza, a 19-year-old Penn State student, had recently accepted an invitation to join Beta Theta Pi, the fraternity’s chapter said in a statement.

Fraternity members told police that Piazza was intoxicated when he tumbled down the basement stairs Thursday night, the State College police said in a news release. He was unconscious when officers found him inside the Beta Theta Pi house. Piazza was eventually transported to a hospital, then flown to a second medical facility. He was pronounced dead Saturday morning.

“Penn State released that one of their students had died as a result of a fall. And that was it, so I assume most people thought, ‘Well, he fell, they called an ambulance, and he went to the hospital and unfortunately died,’ ” Robb told The Post. “Well, that’s not the story. The story was he fell, they waited 12 hours with him and finally called. Hence why we’re investigating why it took 12 hours for them to call.”

Robb told reporters Monday that fraternity members were cooperating with the investigation. Police were reviewing video obtained from inside the fraternity house to try to determine Piazza’s “state of mind” and were working to figure out how long he had been unresponsive before authorities arrived, he told The Post.

“This is a sad affair here,” State College Police Chief John Gardner told the Centre Daily Times. “We’re working through this but also being respectful of the family at this point in time.”

Lisa Powers, a Penn State spokeswoman, said Piazza was an engineering major from Lebanon, N.J.

“Our deepest sympathy goes out to Tim’s family and friends during this mournful time,” Powers said in an email.

Powers wrote that the university’s Interfraternity Council, the governing body for Penn State fraternities, placed the chapter on a temporary “cease and desist” until the investigation, and “any potential related conduct process,” is wrapped up. That means the chapter can’t host or participate in fraternity or sorority activities, she said, including pledge activities.

“It is no longer considered a recognized student organization,” she wrote.

That was also noted in the statement posted to the chapter’s website, which said that “the University and General Fraternity have temporarily suspended chapter operations” during the investigation.

“It is believed that Tim’s death stemmed from an accidental injury sustained from a fall in the chapter house,” the statement said. “We are working closely with our General Fraternity to determine how this happened, and are fully cooperating with police and Penn State administrators in their own investigations. While additional statements and information will be released once confirmed, our thoughts and prayers are with him and his family during this difficult time.”