LANCASTER Co. Pa. (WPVI) -- The NTSB released its preliminary report on the plane crash in Lancaster County in March.
The agency says the pilot heard a loud pop during takeoff and realized the plane's cabin door had opened.
A passenger tried to hold the door shut while the pilot looked for a place to land.
The plane then started shaking before crashing.
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The pilot and one passenger were seriously injured. Three other passengers sustained minor injuries.
The plane crashed into the parking lot of a retirement community, shortly after taking off from Lancaster Airport.