The fire occurred at around 4:30 a.m. in the penthouse of the Snow Building at 331 W. Main St.
Authorities said there were no injuries. The owner of the penthouse, the only residential part of the building, was out of town, they said. Officials said there was smoke and water damage in other parts of the building.
Defense attorney Mark Edwards spent most of the morning airing out damp files and computers. He said he has to get ready for a court hearing Thursday afternoon.
"I'm trying to get back to my real job instead of playing 'water sucker-upper,' " he said.
The Snow building was built in 1933. Durham Fire Marshal Julius Richmond said firefighters had ruled out an electrical cause for the fire and were investigating other possible causes.