A plantation fire that blazed through Pines Beach in north Canterbury yesterday is being treated as suspicious.
Police are now asking anyone who may have noticed any suspicious activity in the area to come forward.
The blaze began in a plantation forest area 300m north of the car park at Pines Beach, 4km east of Kaiapoi, just before 2pm yesterday.
A helicopter equipped with a monsoon bucket and 21 fire engines battled the fire, which at its peak saw the evacuation of 40 nearby homes.
Residents were allowed back into their properties at 6pm last night after emergency services managed to contain the fire, and the cordon was reduced to encompass the bush and plantation area, acting Inspector Phil Dean said.
"The Fire Service spent a further two and a half hours damping down hot spots.
"The prompt reporting of this fire to emergency services undoubtedly prevented properties in the area being damaged by the fire."
Anyone who may have seen any suspicious activity near the intersection of Kay Ave and Batten Grove between 1pm and 2pm yesterday was asked to contact the police.
Mr Dean said any witnesses may be able to provide information that would help with police investigations.
Anyone with any information can contact police on (03) 313 6167 or information could be provided anonymously by calling Crimestoppers on 0800 555 111.
Meanwhile, police were yet to confirm whether a house fire on Batten Grove was caused by the plantation fire.
Yesterday, fire investigators were at the scene of the house fire, hoping to establish whether the fire began as a result of the the forest fire, or if it was a separate incident, southern fire communications shift manager Riwai Grace said.