Detectives on Wednesday raided and pitched camp at the offices of controversial Nairobi businessman Paul Kobia on Riverside Drive.
The team from Serious Crimes Unit based at the Directorate of Criminal Investigations (DCI) entered the premises in the morning, catching the staff unawares.
For hours, they searched the offices for records and documents, with reports indicating that they were struggling to gain access to safes.
Without giving details, sources at DCI told the Nation that the raid followed a case filed by foreigners.
A small police lorry was seen entering the office compound.
Journalists have been barred from access.