Motorists and pedestrians were warned to avoid the Antrim Street area as police closed off parts of Chapel Hill and Bow Street.
Two Fire Appliances from Lisburn attended the incident, with the Northern Ireland Fire and Rescue Service reporting that it believed the fire had been set deliberately.
A spokesperson for the NIFRS said: “Firefighters were called to a fire on the second floor of an unoccupied building.
"They used two jets to extinguish the fire.
"The incident was dealt with by 2.18pm and the cause of the fire is believed to be deliberate ignition.”
It is understood that the police have since reopened the roads.