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Casey Christie / The Californian

Andrew Swick, National Transportation Safety Board aviation accident investigator, holds a news conference Thursday afternoon near Wednesday's helicopter crash site near Delano. The scattered helicopter parts ended up in the grape vineyards behind Swick.

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Casey Christie / The Californian

Sections of the small helicopter that crashed Wednesday morning are seen in this grape vineyard near Delano during Thursday's news conference by the National Transportation Safety Board near Delano.

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Casey Christie / The Californian

Andrew Swick, aviation accident investigator with the National Transportation Safety Board, left, walks journalists out of the grape vineyard after Thursday afternoon's news conference regarding the helicopter that crashed in this area Wednesday morning near Delano.

No answers were available Thursday regarding what caused the helicopter crash that killed 62-year-old pilot Karen L. Johnson.

What's known is that Johnson and the pilot of another helicopter had performed frost control over citrus Wednesday morning and were returning to their home base in Delano when Johnson's helicopter descended into fog and then crashed, said National Transportation Safety Board investigator Andrew Swick. The other pilot saw Johnson go down and then saw a light glow through the fog, apparently from the helicopter catching fire after it crashed.

The helicopters had been traveling at about 1,000 feet above ground level when Johnson plummeted and hit the ground just north of Spangler Road, a half-mile west of Famoso-Porterville Highway, Swick said. A preliminary investigation report is expected to be released within five business days, he said.

Johnson, of Camarillo, flew for San Joaquin Helicopters.

Swick said investigators will transport the pieces of the helicopter to a facility in Madera on Friday for further examination. He said they've recovered all the major structural components.

He said it could take six months to a year to determine why the helicopter crashed. This particular helicopter did not have a black box, a device which records information about the craft and can be used later to further an investigation in the event of an accident.