A federal investigation into the crash of an Island Hoppers tour plane on Mauna Loa last year did not find any mechanical cause, the Hawaii Tribune-Herald reported.

The release of the federal National Transportation Safety Board's "factual report" is a preliminary step in determining the cause of the June 17, 2008, crash that killed a pilot and two visitors.

According to the report, "no evidence of any mechanical discrepancies was found with the airplane's airframe or engine that would have prevented normal operation."

An autopsy of the pilot, 40-year-old Katsuhiro Takahashi of Kailua, Kona, found no traces of drugs in his system, except for those used to treat high blood pressure. He died upon impact from brain trauma. Takahashi's passengers were Masako and Nobuhiro Suzuki of Japan.

Senior NTSB air safety investigator Jim Struhsaker said the final determination of probable cause would come from the board in Washington, D.C., in two to six weeks.