Lima, Peru ? The missing flight data recorder from a Peruvian airliner that crash-landed last week has been recovered, turned in by a man who scavanged it from the wreckage, a prosecutor said Tuesday.

Cesar Arroyo told The Associated Press that the man, Cesar Cabello, had taken the data recorder home but handed it over to civil aviation investigators Monday in exchange for a $500 reward posted by TANS Peru airlines.

“The box was opened but apparently had not suffered any alteration, (and) the optic fiber it contained hadn’t been damaged,” Arroyo said by telephone from Pucallpa, the jungle city near where the flight went down in a marsh, killing 40 people.

The flight data recorder is expected to be key in determining whether wind shear caused by a sudden, violent hail storm was to blame for pushing the plane off course as it made its final descent to land, or whether there was pilot error. Arroyo said the recorder would be sent to the United States for analysis.