The drivers are taking similar action to Ministry of Food Production employees who refused to work yesterday.
The Public Transport Service Corporation (PTSC) has said it is looking to normalize the situation.
Public Services Association (PSA) president Watson Duke visited the building that Ministry of Food Production employees and bus drivers occupy where he noted a number of structural issues, including locked fire escapes.
According to reports workers at the ministry said that over the years several workers have died from cancer.
The union has called the building to be inspected adding that there were 460 more buildings occupied by public servants which they will be looking at them.