ALMA, Mich. (AP) — The National Transportation Safety Board’s investigation into a small plane crash in Lake Michigan last summer that killed four people has focused on fuel system debris.

The Morning Sun of Mount Pleasant reports Friday recently released documents indicate debris in the fuel filter and another fuel system part.

Photos also were released. A final report is pending.

Investigators have said the plane’s engine lost power July 23 about 10,000 feet above the middle of Lake Michigan while heading from Alma to the Mayo Clinic in Rochester, Minn. Pilot Jerry Freed reversed course but crashed about five miles from Ludington.

Freed was the only survivor. He had volunteered to fly Don Pavlik, the Alma schools superintendent who was to receive cancer treatment, to Rochester.

All on board lived in Alma.

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