After a squirrel’s interference with a Sullivan substation left campus without power for almost two hours Tuesday, Jack Colby, associate vice chancellor for Facilities Operations, said he does not think it could have been prevented.

A chain-link fence surrounds the substation, and the area is graveled and separated from trees to keep animals away, he said. But according to Colby, a squirrel crawled across high-voltage conductors in the substation, triggering the blackout.

“Why this animal was there, we have no idea,” Colby said.

The campus has faced power outages before, and, according to Capt. Jon Barnwell of Campus Police, they are usually caused by a glitch in power grids — power surges that blow out transformers or animals that get into high-voltage power distribution areas.

If something gets into the area and causes a machine to overheat, Barnwell said, the device will shut down for its own safety.

Buildings on campus have emergency generators or battery-powered emergency lights in case of a power failure, Colby said, but some residence halls’ emergency lighting did not function Tuesday.

“There was a faulty circuit board in the emergency transfer switch that provides power to the Tri-towers,” Colby said.

According to Colby, the faulty equipment was replaced Wednesday.

While some residence halls were evacuated after their emergency lighting did not turn on, including Tucker and Carroll halls, Barnwell said that was a decision on a “Housing level,” and Campus Police did not order any evacuations.

Its primary concern, he said, was retrieving people who were stuck in 11 elevators across campus with its fire protection division, the Raleigh Fire Department and elevator specialists.

Barnwell said he was pleased with the response from the University and from students.

“We did our best as a University to expedite [the repair] and get [campus] up and running,” he said.