A wide swath of Harvard's campus, including all the river houses and the Kennedy School, was blacked out for 10 hours Tuesday by an electrical fire in the basement of Old Quincy.

According to Harvard Director of Engineering and Utilities Harold A. Hawkes, the fire was caused by a short circuit in an electrical switch.

"It was a high voltage electrical switch at the electrical substation in old Quincy. It failed, which caused the fire," Hawkes said in a telephone interview Tuesday. "It caused two circuits to trip out, which caused power outages in 12 buildings."

Hawkes said the buildings affected include Lowell House, Standish Hall, the entire Kennedy School, Kirkland House, Eliot House, Gore Hall, McKinlock Hall, Old Quincy, Mather House, 29 DeWolfe St., Dunster House and Rosovsky Hall.

The fire also cut off e-mail access to all Harvard buildings between Mass. Ave. and the Charles River.

According to Hawkes, there were no injuries and little damage to Quincy House from the fire.

The switch itself, which Hawkes said is "about the size of a good-sized refrigerator," was destroyed and will have to be replaced.

Hawkes said the effect of the short circuit was "a ball of fire in the contained area" of the switch, a type of blaze that "usually self-extinguishes pretty quickly."

Although the Harvard Police and the Cambridge Fire Departments were both called to the scene, Hawkes said the fire was contained fairly quickly.

Indeed, the damaged switch was isolated and power was restored to all buildings but Old Quincy by 2 p.m.

Repair workers ran temporary power cables into Old Quincy, but planned to restore full power to the building by Wednesday.

Hawkes said this type of problem, while uncommon, is not unheard of. Such accidents are "pretty much unpredictable," he said.

The loss of computers, phones, air conditioning and lighting during business hours caused some minor problems for students and administrators on campus.

Roger A. Storey, associate director of career services at the Kennedy School, said his office was forced to make accommodations for its summer students.

According to Storey, one program was shifted to the Business School for the day. But the 240 students in a mid-career summer program were not so lucky. Storey said there were too many of them to move to another part of campus.

"The first classes were held as best as possible, some meeting outside, some in partially lit rooms," Storey said. "But it became too warm, too uncomfortable. We canceled classes for the day."