Police received a report of a fire in Sandringham, Craigavon at 11.23pm on Wednesday, 27 April.
Officers attended and found that a car had been set alight. The fire spread to another car and a nearby house, causing damage to the two vehicle and dwelling.
Detective Inspector Gawley said: “We would like to hear from anyone who noticed any activity in this area in the hours prior to this incident or even the days before.
“We can be contacted on 101, quoting ref: 1354 270416.”
If you prefer to provide information without giving your details you can contact the independent Crimestoppers charity anonymously on 0800 555 111.