The PSNI has launched investigation into what it described as a "significant blaze" in the Waterside area of Londonderry.
The fire was started around 8pm on Tuesday evening in Dunfield Terrace. A number of unoccupied properties were set alight.
The fire was brought under control by the Fire Service during the night.
No one was injured during the fire however, neighbouring houses were put at risk.
Police Inspector Swanson said: "If not for the work of the NIFRS, however, the outcome could have been different for residents in the immediate area and their homes."
The PSNI appealed for anyone with information about the fire or who noticed suspicious behaviour in the area to contact investigating officers.
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