Police in Isiolo town have detained eight Co-operative Bank staff linked to the loss of Sh26 million, stolen by three suspected robbers.
County police boss Charles Ontita said CID officers established that one of the cashier opened the bank's back door to let in the robbers who were armed with an AK47 rifle and a panga.
They tied the staff with ropes and made away with the money.
The 6.30pm incident happened when no security officer was around.
According to Mr Ontita, the staff, who are currently booked at the Isiolo police station, will aid in the investigation.
Mr Ontita also revealed that preliminary investigation, based on the CCTV footage, confirmed that it was an inside job.
"We did not get clear explanations on how the safety keys changed hands from the operation manager to the suspects, but we are still interrogating the staff for more leads," he said.