PETALUMA (AP) — Northern California authorities say a pilot and passenger have been killed in the crash of a small plane near a Sonoma County airfield.

Witness Giorvi Alvarez tells the Santa Rosa Press Democrat that he heard the plane’s engine sputter shortly after takeoff Sunday from Petaluma Municipal Airport.

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Alvarez says the plane was turning around and heading back to the airport when it crashed in a street. Officials say nobody on the ground was hurt but both occupants of the plane were killed. They haven’t been identified.

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Federal Aviation Administration spokesman Allen Kenitzer says the plane was a single-engine Van’s RV-6. The two-seat homebuilt airplane is sold in kit form.

The FAA and the National Transportation Safety Board are investigating the crash about 40 miles (64 kilometers) north of San Francisco.

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Copyright 2018 The Associated Press.