It is not unusual for wreckage and human remains to be uncovered at different stages at crash sites, the Transport Accident Investigation Commission says.
Yesterday, police said human remains found on Fox Glacier were that of a British tourist who was among seven people killed in a 2015 helicopter crash.
The remains of Cynthia Charlton, 70, from Hampshire in the United Kingdom, were found by a tramper on 2 March.
Seven people were killed when the Alpine Adventures squirrel helicopter crashed on 21 November 2015.
The commission said it recovered the crucial parts of the helicopter after the crash.
"The engine was sent to the United States for inspection by the engine manufacture under the direct supervision of the commission's investigator in charge.
"This is a normal procedure and not unusual.
"The engine is now back at the commission's technical facility in Wellington. Since then, other components of the flight control system have been tested and inspected in Australia.''
A team from France inspected the wreckage in Wellington.
"The evidence-gathering phase has ended and work is now under way on the preparation of a draft report," the commission said.
"It's not unusual for wreckage on a glacier like the Fox to become uncovered at different stages, given summer melting and glacial movement.
"The commission was aware that some human remains were not recovered when the investigation first began. Body recovery is a police matter.''
The police could not say if any more human remains from the crash remained on the glacier.
After the crash, the Civil Aviation Authority grounded Alpine Adventure's fleet of helicopters because of safety concerns. It charged the company's owner, James Patrick Scott, and quality assurance manager Barry Waterland.
Both men have pleaded not guilty to the charges under health and safety legislation.
A trial date has not been set.