The California Highway Patrol's initial reports indicated the collision occurred shortly before 7 p.m. in the 5100 block of Highway 29, just inside Napa County.
There were not many details about the crash available Thursday evening.
However, reports from the scene indicated a young woman's arm was severed because of the single-vehicle collision.
The vehicle and the two people riding in it made it to the Middletown Fire Station, which was where a REACH air ambulance picked up the female to fly her to a trauma center, according to the CHP.
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