There have now been 10 deliberately lit vegetation fires in Wanaka's central township since January 9, with Monday's fires occurring between 2.13am and 2.37am.
The district is on a high fire alert, with the risk rating likely to be lifted to extreme later this week if the ongoing spell of hot temperatures continues.
Police are pleading for public help to catch the culprits and say people can use the anonymous 0800 555111 Crimestoppers line if they are concerned a flatmate, friend or family member might be involved.
Queenstown fire safety officer Stu Ide was particularly concerned one of Monday's four vegetation fires was set in a private garden on Meadowstone Dr, about 25m from a house and the Elmslie House retirement village.
Elmslie has accommodation for 18 residents, hospital facilities for 12, and seven apartments.
"This is really what's worrying us, this safety aspect. A fire that takes off through scrub and grass and threatens people living in houses. Of more concern, one of the fires was set close to the retirement village where people can't move in a hurry," Mr Ide said.
Elmslie House manager Penny Fisher said yesterday she was aware of the New Zealand Fire Service's concerns and was to discuss them with residents yesterday.
"I am not sure they are completely aware. And I will be letting the staff know and keeping an eagle eye out. I don't want to upset the people who live here. It can be quite worrying. They like to know they are safe," Mrs Fisher said.
The Meadowstone Dr house occupant could not be contacted for comment.
Another fire melted a blue wheelie bin on Pembroke Park, near a temporary outdoor cinema screen, which Mr Ide said was also concerning because plastic combined with the bin's contents of bottles and rubbish was extremely combustible.
Wheelie bin fires created a flowing fuel fire, spreading easily "almost like a petrol", he said.
The other fires were in grass on Upton St and near the corner of Upton St and McDougall St.
Mr Ide said it appeared the fires had been set in the same manner and shared other similarities with the first six fires last month on the corner of Chalmers St and Stratford Tce.
One of those fires destroyed a Ford Falcon station wagon.
Mr Ide stressed the culprits would face heavy penalties if convicted of arson.
He reiterated earlier calls for public vigilance and to report any suspicious behaviour.
"If they see anything, they've got to report it because property and life are at risk here," Mr Ide said.
Senior Sergeant Allan Grindell said yesterday Crimestoppers was an independent charity and very successful in the United Kingdom.
It provided information to police but did not pass on details of sources.
"If it leads us in the right direction, it is all very important. It [the culprit] might be a family member or a flatmate. They might not want to dob them in with a name," he said.
Information provided by the public yesterday was being investigated but no arrests had been made, he said.
Snr Sgt Grindell said it was not easy to pinpoint exactly what order Monday's fires were set as some could have smouldered.
"But the four are obviously related and probably set off within a short time of each other," he said.
Snr Sgt Grindell was keeping an open mind on whether the same person lit all the fires but acknowledged they shared similarities.
- The Queenstown Lakes District Council is in a "state of readiness" to issue an extreme fire risk warning and is not issuing any fire permits, principal rural fire officer Gordon Bailey said yesterday.
"I would think another few days of this (weather) and we would be there, really," he said.
