Police are piecing together information about the rare robbery.
The thugs are said to have used gas cylinders to break into safes and had time to eat inside the banking hall.
Customers who turned for the normal services were directed to other branches in Nairobi’s Westlands and Industrial areas.
Increased bank robberies are on the rise; in November last year, thugs broke into Kenya Commercial Bank, Thika branch escaping with Sh50 million.
The thugs accessed the branch and removed five containers of 50-real notes, with an estimated value of Sh50 million. They disabled the bank's internal alarms and sensors.