Police are urging anyone with information on four fires which were deliberately lit in Blenheim last Friday to come forward.
The series of fires were located in the south and southwest areas and lit between 6pm and midnight.
A further three fires were being investigated from earlier in the week.
Acting area commander Detective Senior Sergeant Ciaran Sloan said while the recent fires had not caused significant damage they were close to houses and had the potential to endanger lives.
"At this stage we're just lucky there has been no serious damage.
"There will be someone out there who knows who is responsible and they need to contact police," he said.
Anyone with information should call Blenheim police 03 5785279 or on Crimestoppers 0800 555 111.