Power has been restored after an outage hit the entire Stony Brook University campus and hospital system Thursday afternoon, authorities said.

The problem did not affect patient care at Stony Brook University Hospital, but most night classes on the main campus have been canceled, officials said.

Power was restored by 4:30 p.m. to all but 11 buildings on the university side of the school-hospital complex, which is separated by Nicolls Road, officials said.

"Campus operations responded and is working diligently to assess and repair the malfunction," said university spokeswoman Lauren Sheprow.

At 7:50 p.m., electricity was back on in the 11 buildings, the school's website said.

A shortage in part of the power feeder system had knocked out electricity just before 3:41 p.m., and that at first affected only the 11 buildings, she said. Those included several dorms, the life sciences building and the Javits Lecture Center, the university website said in updates on the outage.

The feeder system of lines carries electricity from a generating station to the power distribution system.

But during repairs, the rest of the campus and the hospital suddenly lost power also, Sheprow said.

Backup generators, including those at the hospital, immediately kicked in, university and hospital officials said.

The cause of the systemwide outage is not clear, but officials are looking into it, Sheprow said.

The university has its own power system and does not use PSEG Long Island.

At Stony Brook University Hospital, computers and hallways went dark for a few seconds at about 4 p.m., but no patients in surgery, the intensive care unit and other areas were in danger due to the backup power, said hospital spokeswoman Melissa Weir.

Full power to the hospital returned in less than 30 minutes, Weir said, adding, "It was restored really quickly. Nothing was disrupted."

Just before 5:15 p.m., university police Chief Robert J. Lenahan sent an alert saying classes that were to begin 5:30 or later on the main campus were being canceled. Only classes in the health science center on the hospital campus and the basic science tower would be held as usual, according to the alert, emailed by the university's emergency operations center.

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