The couple, in their 50s, has also contacted the Civil Aviation Authority (CAA) to ask what they thought it might be.

A CAA spokesman confirmed the conversation took place, but was not officially recorded.

"If someone wants to 'make it official' then we ask them to email us with details - in the case of UFOs we would usually tell them that if there was something untoward then we'd expect Airways or pilots to have something to say.

"In the absence of any such reports we won't be investigating it - although we are happy to record it," the spokesman says.

The representative who spoke to the couple suggested it could be drones or an approaching aircraft, but "the caller was adamant those could not be the cause".

Ms Rasmussen has taken hundreds of photos of the objects which stay around their isolated Awhitu property, where they've lived for 12 years, "all night long".

She says they normally hover just metres above their roof and make no noise.