Engineers are evaluating the safety of the University of Minnesota's Northrop auditorium after part of the nearly century-old building's roof collapsed Wednesday night.

The university's dispatch center received a call about 7:30 p.m. from facilities workers who were in the building, heard a loud noise and "thought it could have been an explosion," said university spokesperson Chuck Tombarge.

University police and city firefighters responded, shined a light on the auditorium and found a hole along the roofline on its southeast corner. The hole is over an attic and utility space.

"Certainly, it is problematic as it's open to the outside," Tombarge said. "There are structural questions, but also questions about how do we keep the pipes from freezing."

The collapse happened days after a storm dropped about 15 inches of snow on the Twin Cities. Tombarge said engineers and other health and safety workers at the university spent Thursday inspecting the auditorium as well as the nearby Church Street and Northrop parking garages. All three of those buildings have been closed while the inspections are pending.

It was too early Thursday to know the precise cause of the collapse or how much it might cost to repair the damage. "I think the priority here is to make sure the building is safe before we allow any occupants or events back in," Tombarge said.

The university said it didn't receive any reports of injuries related to the collapse.

The U's College of Science and Engineering had been hosting Physics Force events at the auditorium this week. The program brings together a group of high school teachers and U professors to perform science demonstrations for kids. The group's shows, which had been scheduled to run through Saturday, have been canceled.

The next scheduled events are the Joffrey Ballet on Jan. 20-21. Ticket holders can contact the Northrop box office with questions, the university said.

"Event organizers will also proactively update participants as needed," a Northrop announcement said.

Northrop was built on the East Bank between 1928 and 1929 as part of a major university expansion project. The building named in honor of the university's second president, Cyrus Northrop, opened Oct. 22, 1929, and since has hosted world-renowned dance performances, concerts, civic events and graduations.

The building underwent a $21 million exterior restoration in 2006. The interior received a three-year, $88.2 million renovation before reopening in 2014, its last major update.