The National Transportation Safety Board remains on the scene of Friday's fatal plane crash about six miles northeast of Bowie.
NTSB Spokesman Terry Williams says a preliminary report as to what may have caused the twin-engine Cessna to crash is expected to be released next week.
Williams says investigators are examining the plane's engine and flight controls, and they're documenting the scene off Highway 59, about a mile north of Bowie Municipal Airport.
He says the wreckage will soon be moved to a secure location for further examination.
Also, Williams says they've interviewed two people who witnessed the crash, and plan to interview pilots who flew into Bowie Municipal Airport before the crash.
Lawrence Liptack, 51, of Manvel near Houston, and his 10-year-old son, Landon, were killed in the crash.
Liptack's wife, a high school principal, was not on board the plane.
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