Robbers over the weekend broke into the Habib Bank AG Zurich along Koinange Street and made away with an unknown amount of money.
The robbers entered the bank through the rear door on an indefinite period, went into the second floor of the building and disabled the alarm and the CCTV surveillance cameras before getting into the banking area.
While inside, they used gas and wielding machines to break into the safes and made away with an unknown amount of money before attempting to break into the strong room.
Nairobi County Commander Joseph Ole Tito said the robbers used papers to block the bank's tinted glass windows so that security guards could not see what was happening.
"They took their time because we have found food leftovers meaning they even had the time to eat inside the bank. They have really done a lot of destruction inside there, but they did not manage to get into the strong room," Mr Tito said.
The left-overs of githeri, beef, chicken, rice and chips which were in disposable plates were found on the counters and on the floors.
The strong room, according to one of the officers, contained Sh41 million which was still intact by the time detectives opened it on Monday morning.
Mr Ole Tito, Nairobi County Director of Criminal Investigations Ireri Kamwende, Central DCIO Samuel Kobinas, Central OCPD Robinson Thuku and other senior police officers were investigating the robbery.
Mr Tito said they suspected that the robbery was staged by people familiar with the bank.
"This must be an inside job, by people who knew how to access the bank through the rear gate, the location of the CCTV cameras, the alarm, the safes and the strong room," Mr Tito said.
Clients were not allowed into the bank, but asked to go to the Westlands and South B branches. Some employees who arrived for work were interrogated by the detectives.