FAAd spokesman Jim Peters says the pilot of the six-seat Cessna Citation C-525 declared an emergency minutes after taking off but was unable to fly to safety.
He says the plane was registered to Jeanette Symons of San Francisco, but the identities of the victims were not confirmed tonight.
Peters says the plane took off at 5:45 p.m. bound for Lincoln, Nebraska.
A few minutes later, the pilot told an air traffic controller there were problems with the indicator that tells how level the plane is. The controller then saw the plane descend rapidly on a radar screen.
Inspectors from the National Transportation Safety Board and the local FAA office were expected at the crash site on Saturday.