Investigators looking into the helicopter crash that killed Kobe Bryant and his daughter Gianna say there is no evidence of a 'catastrophic internal failure'.

The interim report issued by the National Transportation Safety Board (NTSB) 12 days after the accident also said examination of both rotor assemblies found damage "consistent with powered rotation at the time of impact."

The preliminary findings pointed to no obvious signs of mechanical problems that may have contributed to the fiery crash on January 26.

New images have been released by the NTSB which show the doomed helicopter moments before the crash that killed everyone on board.

The death of Bryant, an 18-time all-star in the National Basketball Association and one of the world's most admired sports figures, prompted an outpouring of shock and grief from fans and fellow athletes around the globe.

The retired Los Angeles Lakers forward had been on his way to a youth basketball tournament in which he was coaching and his daughter and two other girls aboard the luxury chopper were due to compete.

The report did not rule out that mechanical issues might yet be identified when the engines and other parts recovered from the wreckage of the Sikorsky S-76B are disassembled and more closely examined.

NTSB board member Jennifer Homendy said two days after the tragedy that clouds, fog and limited visibility reported in the vicinity of the crash would be a key focus of the investigation.

Videos and photographs taken by the public in the area depict fog and low clouds obscuring the hilltops around the crash site, including security video footage showing the helicopter disappearing into clouds moments before it went down, according to the report.

The NTSB also quoted a witness from a mountain bike trail in foothills surrounded by mist who recounted briefly glimpsing the helicopter emerging from clouds as it rolled to the left before crashing seconds later a short distance away from him.

The pilot, an experienced aviator certified as an instructor, was navigating by visual orientation, not by instrument guidance, during the entirety of the ill-fated flight, the NTSB said.

"An experienced but nevertheless single pilot in bad weather is a bad formula for the safe operation of a helicopter," he told Reuters.

Shortly before radar contact with Bryant's helicopter was lost, the pilot had told air traffic control he was trying to climb above a cloud layer, the NTSB said.

Moments later the aircraft banked to the left and began to descend, slamming into the ground at more 45 miles per hour (72 kph) and bursting into flames.

"The entire fuselage/cabin and both engines were subjected to a post-crash fire," the report said.

The wreckage, strewn about an impact crater, was found in the foothills of the Santa Monica Mountains near the town of Calabasas, about 40 miles (64 km) northwest of downtown Los Angeles.

The agency said the conclusions it reaches on the cause of the crash and contributing factors will be published in its final report, which is expected in 12 to 18 months.