The plane was preparing for departure from RWY03L with 185 passengers on board when the incident occurred at approximately 22:40 on Sunday.
Four ground-handling employees who were in the building at the time experienced minor injuries and no injuries were reported on board the plane.
The South African Civil Aviation Authority (SACAA) confirmed the incident and SACAA spokesperson, Phindiwe Gwebu said the preliminary report indicates the aircraft used the wrong taxiway.
"The BA 747-400 aircraft was cleared for takeoff on Runway 03L. The SACAA confirmed that the air crew got instructions from the Air Traffic Control to taxi using taxiway B," Gwebu said.
"The crew continued onto taxi way M which is narrower resulting in the aircraft impacting on an office building behind the SAA Technical hangers.
Four officials who were in the building were injured by the debris from the building. The 17 Crew and 185 passengers who were in the aircraft escaped unharmed and were evacuated from the aircraft through door no. 5."
The report also indicated fuel spillage from the aircraft but this was contained by the airport fire services without further incidents.
Gwebu confirmed that SACAA investigators were dispatched to the airport on Sunday night and early on Monday morning where they witnessed the recovery of the aircraft as well as the removal of the flight recorder from the aircraft.
Acsa confirmed the aircraft has since been moved to a remote location and operations have not been disrupted as a result of the incident.
BA said it is launching an investigation into the incident and is giving full assistance to the independent South African Civil Aviation Authority (SACAA) with the matter. Civil Aviation Authority (SACAA) with the matter.
The investigation continues.
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BA Plane hits building at OR Tambo pic.twitter.com/j09waXv2Cx
— cutmaker (@cutmaker) December 23, 2013