A fire set at the rear of flats caused damage to four properties. A 19-year old arrested in connection with the incident was bailed pending further enquiries.
Officers are keen to speak to witnesses or anyone who may be able to assist the investigation.
They can be contacted at Downpatrick Station on 0845 600 8000.
Information can also be passed anonymously by calling the independent charity Crimestoppers on 0800 555 111.