The helicopter wreckage from a crash that killed basketball star Kobe Bryant and eight others showed no outward signs of engine failure, the US National Transportation Safety Board (NTSB) said Friday.

Bryant and his daughter were killed when the helicopter they were riding to a girls' basketball game crashed into a hillside on January 26 in Calabasas, California.

The NTSB said in an update to its ongoing investigation that "viewable sections of the engines showed no evidence of an uncontained or catastrophic internal failure."

Camera footage reviewed by the NTSB showed pilot trying to exit clouds by increasing altitude. He managed to ascend to 2,300 feet (701 meters), just 30 meters from the top of the clouds, before starting a rapid descent.

Investigators said they will continue to dissemble and examine the engines, which were engulfed in flames following the crash, adding that a cut tree branch at the crash site indicates the rotors were turning at the time of impact.

However, the report did not rule out eventual mechanical problems that could be identified when the engines and other parts recovered from the wreckage are more closely examined. 

A crash in the fog

Friday's investigative update did not offer any findings about what caused the crash, and the final report is not expected for at least a year.

The NTSB has said fog and limited visibility reported near the crash site would be a key focus of the investigation. The report said the hillside where the accident occurred was obscured by fog at the time of the incident.

Read more: Foggy weather scrutinized in Kobe Bryant crash, say investigators

A witness told the NTSB that the helicopter was flying forward and downward through the fog before it crashed, adding he saw the helicopter for 1 to 2 seconds before it hit the hill.

The Sikorsky S-76 helicopter was not equipped with a "terrain awareness and warning system" device that signals when an aircraft is close to hitting the ground. The aircraft also did not have a black box or a voice recorder.

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