Mbombela - A preliminary investigation has revealed that the collapse of a ceiling at the Mpumalanga provincial government complex building was due to routine maintenance.The provincial Department of Public Works spokesperson David Nkambule said one employee was injured when the ceiling collapsed at Building 7 at about 11:35."A preliminary investigation indicates that a portion of the roof collapsed during a routine maintenance whereby a contractor was installing a waterproofing membrane in the built-in pot plant to prevent leakage," said Nkambule."The portion of the roof which is situated adjacent to the pot plant in Building 7, 2nd floor, collapsed as a result of the soil that was removed from the pot plant and placed on the corrugated iron roof. According to the preliminary assessment, the incident was not caused by any structural defects."Nkambule said a full investigation was already underway."A detailed report will be issued once the matter is concluded. The department would like to assure its employees that their safety and security is a priority and necessary precautionary measures have been put in place to ensure that similar incidents do not occur in the future," said Nkambule.