Six officers at Siaya Prison have been interdicted after a prisoner serving a life sentence escaped last Thursday.
Nyanza region prisons commander Amos Misik said the inmate, a former General Service Unit officer, may have been assisted to escape.
"Our investigations so far indicate it could have been an inside job. We have called in detectives from the DCI to investigate all officers on duty on the fateful day after which action will be taken," he said.
Mirik said the inmate, Francis Musyoka, had been found guilty of robbery with violence.