Investigators are treating a flat fire in Hellesdon on Friday as arson.
Fire and police services were called to Philadelphia Lane at 3.20pm after reports of smoke in the downstairs flat.
Norfolk police confirmed the fire will be treated as arson.
The fire is now out and nobody was hurt but there is smoke damage to the building.
It is the fourth house fire in six days in the north city area.
Although police said it is too early to link the latest blaze to the other three this week.
Officers have, however, been exploring the connections between a fire on Constitution Hill between midnight and 12.35am on Sunday, Shipfield Road between 1am and 1.40am the same day and on Thursday at 3am in St Clements Hill.
Anyone with information should call police on 101.
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