Police are looking for two "vehicles of interest" following a suspicious house fire in the Southland town of Waikaia.
The Elswick Street property went up in flames just after midnight on Wednesday.
No one was injured but the house "sustained extensive damage", Detective Sergeant Brian McKinney said.
Investigators were now looking to hear from anyone who saw either a red vehicle, or a dark-coloured twin cab ute that was towing a trailer around the time of the fire, McKinney said.
"Both vehicles were seen in the vicinity of Elswick Street shortly after the property was set alight.
"The red vehicle was seen leaving Elswick Street and heading at speed towards Riversdale."
Anyone with information could call police on 105 or make a report online at 105.police.govt.nz, clicking Update Report and referencing the file number 240222/8704.
Information could also be provided anonymously by calling Crimestoppers on 0800 555 111, McKinney said.
"The investigation is ongoing, and we would like to thank the people who have come forward so far."