A criminal investigation has been launched into one of the two fires which broke out on the Port Hills in Christchurch in February.
Two separate fires several kilometres apart started on 13 February - the first began on Early Valley Road with the second starting on Marley's Hill.
Two days later they had combined into one large fire that eventually gutted 11 houses and forced thousands of people to evacuate their homes.
Police said investigations had found that the cause of the fire on Marley's Hill was suspicious - with a criminal investigation underway.
The Fire Service said investigations into the Early Valley Road fire were still ongoing.