"We're really just gathering information from all the parts we possibly can to piece together where this drone or drone-like object originated from."
A safety investigation team would sift through the evidence, although the spokesman said he couldn't comment on who the team would speak to.
He appealed for anyone with information to contact the authority.
"We'd be really keen if anybody knows of anybody with a drone of that description."
The spokesman said the authority would play an educational and preventative role rather than take a punitive approach.
Last month new rules came into effect governing the use of unmanned aerial vehicles and the spokesman said this was the first incident of its kind he was aware of since then.
Commercial drone operator Carl Sheppard said he would be surprised if it was a professional drone user behind Friday's near miss.
He thought it more likely an hobby user seeing how high they could fly.
While multi-roter drones might run out of power if they made it to 6000 feet, "plane" models could go a lot higher.
"It's not unheard of to go pretty high. It's usually the people that just want to get the thrill of going high but it's not really that appealing because when you get up there it's just a big empty space and what's the point?"
Mr Sheppard said he had navigational charts so he could see what traffic controllers were doing in a particular area and altitude if he wanted to operate a drone in commercial flight paths.
The airline pilots' union today said it was "very worried" about the near miss.
The Air Line Pilots' Association , which represents 2500 pilots and air traffic controllers, said it was relieved no one was injured and no damage occurred.
"Coupled with an almost complete lack of pro-active education by the Civil Aviation Authority, it is alarming that an uninformed person can purchase a drone and operate it near an aerodrome, seemingly with little idea of the seriousness of their actions should the drone hit or come in close proximity to another aircraft," said association air traffic control director Jon Brooks.
He said drones were creating "additional workload and complexity" for air traffic controllers and pilots.
The union called for compulsory installation of "see-and-avoid technology" on drones, the addition of identity markings on drones, and a comprehensive education programme for all drone operators.
Transport Minister Simon Bridges said the incident was being treated seriously, while in a statement, Air New Zealand said it was disturbed by the "emerging trend of [the] reckless use of drones that puts the safety of customers and staff at risk".
