Police do not believe a spate of arsons across Christchurch in the past few months are linked and are more likely to be "opportunistic''.
They have called on local residents to be on the lookout for suspicious activity around vacant properties.
In the latest incident, a fire at an abandoned house in east Christchurch early today is being treated as suspicious.
A Fire Service spokeswoman said they were called to the house on Buckleys Rd, Linwood, shortly before 1pm.
Detective Inspector Greg Murton said investigations into recent suspicious fires showed they were likely to have been the work of different people and mostly likely "opportunist'' incidents.