The Civil Aviation Authority has not yet established what caused the window of Rod Vaughan's rented light plane to shatter over Waihi last week.
The former TV journalist was forced to make a crash-landing in a field on March 28. He and passenger, son Richard Vaughan, walked away with only cuts and bruises.
Vaughan believed the crash was caused by a mid-air collision with a drone but the authority has yet to find any evidence to back up the theory.
CAA spokeswoman Philippa Lagan said a safety investigator had examined the wreckage and crash site, interviewed Vaughan and talked to Waihi police and mine staff.
She said the evidence to date showed the windscreen had been "compromised causing it to fail catastrophically".
"No other aircraft systems were considered compromised or pertinent to the accident."
Vaughan had done well to land the plane in a safe area, considering the damage.
Lagan said the next steps for the investigation included an area search of the mine for evidence and talking to the aircraft manufacturer.
Vaughan said he doubted "the smoking gun" would ever be found but still believed drone strike was the "most plausible explanation" and was pleased to see investigators taking the theory seriously.
"However, I doubt that it will ever be resolved as no one is going to put their hand up and admit to almost killing two people."
Kit Wilson, senior community advisor for Waihi mine operators Oceana Gold, said he would look for crash debris when flying company drones over the mine, but said it was unlikely anything would be found.
"The pit is over 200 metres deep - 265m from the top of the north wall. Even if the drone is in one piece, there is only a very small chance I would be able to see it."
He said the mine was a popular spot for drone operators - locals and tourists - as they could fly over the pit with little risk of crashing. A drone or two visited most weeks.
The company was fine with that as long as operators followed aviation rules for drones, especially staying under the legal height of 120m (400ft) as flying higher could endanger helicopters.
Wilson said he had made one complaint to the police and the authority about a drone operator flying well above the limit near the mine.
Footage was posted online but as far as he knew, nothing came of the complaints.
The company had three drones, mostly used for aerial photography, but other uses were being considered.
Glenis Gentil, co-owner of Waihi radio station Gold FM, said the station had asked residents to keep an eye out for wreckage.
She said many Waihi people were worried about drone use in residential areas. She had one hover over her while sunbathing in her backyard and another couple felt spied on in their spa.
She said Beach Hop organisers banned drones this year because of the danger they could pose over a crowd.
Tauranga helicopter pilot Glenn Olliff, owner of Oceania Helicopters, said drones were a worry for pilots because they were hard to see and usually did not log flight plans.
He believed a registration system might deter irresponsible use, while Wilson thought compulsory training or licensing for operators might reduce the risk of accidents.