The outage — which lasted less than 20 minutes in some areas and several hours in others, according to some student reports — did not appear to seriously interfere with University operations, officials said. But while some students shrugged the outage off, others who lost power in their dormitories said they were concerned with the vulnerabilities in Yale’s electrical grid.

Facilities officials were still compiling the details as of Thursday evening, but the blackout appeared largely to affect central campus buildings, including Old Campus and Branford, Jonathan Edwards, Davenport, Pierson and Morse colleges. The outages occurred at different times throughout the course of the morning, but most reportedly began before 10 a.m.

Director of Facilities Operations Eric Uscinski said the problem was originally caused by a disruption in the electricity supply — possibly a power surge — coming from United Illuminating, a commercial supplier with a monopoly on the local power grid. Facilities officials had to shut down power in some areas so as to protect the integrity of the system as a whole, he said.

“It was a problem with U.I. that affected our system,” Uscinski said. “We had to do a quick shedding so we could stabilize the system and get it back up.”

The process of restoring power was gradual because the buildings’ electrical systems could not be restored simultaneously, Uscinski said.

Some students said the outage caused inconveniences, including a loss of Internet service in Branford, untimely sprinkler activations by Swing Space, and fire alarms in Pierson and Davenport.

Christopher Andrews ’09 said he was about to take a shower in Davenport when the alarms went off, but left the building to err on the side of safety.

“I was outside for about 10 minutes without my shirt off in my shower gear,” he said. “I was pretty upset.”

Other students said the dormitory outage did not bother them because they were not in their colleges when it occurred.

“I don’t think people were in the buildings that much,” Kaitlyn Sanders ’10 said. “It wasn’t that much of an inconvenience.”

Sanders lives in Swing Space, which did not recover power until the middle of the afternoon, she said. While residential areas appeared to be most seriously affected, there were reports of brief outages in the Hall of Graduate Studies and Mason Laboratory on Science Hill.

Yale has experienced several outages over the last couple of years that facilities officials have attributed to external power sources. United Illuminating is generally a reliable supplier, Uscinski said, but utilities staff are working with the company closely to minimize future occurrences.

“The utilities group will be working with them to detail exactly what happened,” Uscinski said. “There is concern when there’s any kind of power loss around here.”

Rayyan Kamal ’09 said that while the blackout did not inconvenience him personally, he was surprised that the effects were so widespread. He thought that Yale had a more resilient system given the University’s prestigious reputation, he said.

United Illuminating could not be reached for comment Thursday evening.