A blaze said to have been started when the oil tank of a house was set on fire is being treated as suspicious by police.
Officers said that shortly before 4.30am they received a report that an oil tank had been set alight at Manor Park in Newtownards.
Emergency services arriving at the scene found up to three oil tanks on fire, with the flames damaging nearby buildings and cars.
There were no reports of serious injuries, but a number of people suffered from the effects of breathing in smoke.
Fire crews said the flames destroyed two cars and a garden shed containing budgies, while four houses were damaged.
Fire-fighters also said they were faced with flowing oil that was alight and could have spread to other properties had it not been dealt with in time.
Police appealed for anyone with information to come forward.