The National Transportation Safety Board investigator, Wayne Pollack, wrote on the agency's website there's no evidence of a problem with the engine, oil leakage or fire.
The Seattle Times reports the investigation continues and likely will take several months.
Three people were killed when the single-engine Cessna crashed in the early morning hours of Feb. 15.
Radar showed the plane took off from Renton, climbed to 2,400 feet but descended to 1,500 feet as it approached Snoqualmie Falls.
A friend of one of the passengers told The Times they had attended a hockey game that evening and apparently took the plane ride for fun.
More Northwest Headlines
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