Business at Workers House on Kampala road came to a standstill after discovering an object believed to be a bomb on the 11th floor.
Kampala Metropolitan Police spokesperson Ibin Ssenkumbi says investigations are still going on to find out what the object is and who could have left it in the building.
Police counter terrorism Unit sealed off the whole Workers house building and heavy deployment has been very evident for most of Monday.
Roads around the area were also been sealed off although it was not clear by press time whether the item was a bomb or not.
The police has in recent times warning of possible terror attacks by al-shabab who have been targeting Uganda for deploying troops in Somalia.