A mysterious large explosion sound has been heard in several towns in North Canterbury.
The incident happened just before 9am on Tuesday, with many residents saying there was a shockwave following the noise.
A police spokesperson said they received calls from people in Kaiapoi, Rangiora and other North Canterbury areas, but most were from Woodend, 23 minutes north of Christchurch.
The spokesperson said police looked for the source of the sound but were unable to find the cause. They asked anyone with information to call 105.
A Fire and Emergency New Zealand spokesperson said they had received no call-outs for an explosion in the area and a Transpower spokesperson said they were not aware of any problems at the Kaiapoi substation.
Joe Fraser was mowing lawns in Woodend when the explosion sound happened. He said it was so large, a woman driving by stopped her car because she thought the motor had blown up.
On social media, many residents reported hearing the mystery noise.
One person said it sounded like a sonic boom, while another said it sounded like a gas explosion.
- This story was first published by Stuff