About 100 firefighters responded to the fire, Miller said.
The building at 1425 Philadelphia Ave. is part of a complex owned by Menno Haven, a housing center for seniors in Chambersburg. Some of the 100 residents, whose rooms in the facility next door were closest to the fire, were moved as a precaution, officials said. None of the residents were injured.
Robbie Gable, spokesman for the Chambersburg Fire Department, said the fire is believed to have started in the basement and worked its way into the ceiling. "It was a working situation when we got here," he said.
A state police fire marshal was expected to try to determine the cause of the fire later Thursday, officials said.
Fire police detoured traffic around the Menno Haven complex at 1425 Philadelphia Ave.
Construction crews had been gutting the interior of the building in preparation for its renovation into 55 apartments that are scheduled to open in April 1998, said Conrad Beachley, executive vice president and acting CEO of Menno Haven.
Beachley said he didn't expect damage to be too severe because the construction project is still in the demolition phase.
The building has been vacant for about a year, Beachley said. Until then it had been rented to the federal Depot System Command, said Carol Fries, director of marketing for Menno Haven.
The building and two others at Menno Haven made up the campus of Penn Hall, an exclusive girls prep school, until 1972, Fries said. Wilson College, which adjoins the property on the south, bought the Penn Hall holdings in 1972 but did nothing with them.
Menno Haven bought the Penn Hall properties from Wilson in 1991, renovated the largest building into the 100-unit apartment complex, and later added 85 independent living cottages for senior tenants, Fries said.