SANTA ROSA (CBS SF) — Two people aboard a single-engine plane that crashed while approaching an airport in Sonoma County Thursday evening have died, fire officials said.

The plane, a Piper PA-24, “crashed under unknown circumstances on final approach to Charles M. Schulz-Sonoma County Airport,” Federal Aviation Administration Pacific Division spokesman Ian Gregor said Thursday evening.

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The plane departed from Palm Springs for Santa Rosa with two people on board.

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Santa Rosa Fire Department officials said the plane crashed just before 7 p.m. about 2.5 miles south of the airport.

Fire officials confirmed that the two occupants have died.

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The FAA and the National Transportation Safety Board will investigate the crash, Gregor said.