Emergency services responded to a call about a fire at derelict Africa House on Woodbourne Road, Douglas, at just after 6.15pm last Friday.
Police are treating the blaze as suspicious.
On Monday they confirmed that a local male had been arrested on suspicion of arson. They were subsequently bailed pending further inquiries.
Police say they are waiting for the fire service to complete its fire investigation report.
This could mean it will be some weeks before any update can be given.
Africa House remains in a dangerous condition and the public are being strongly urged not to enter the grounds of the property or the house itself.