The German newspaper Bild claimed its reporter Axel Lier witnessed the helicopter crash during a federal police training exercise. He told the newspaper everyone was "totally shocked" by the incident.
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The 17-year-old was trapped for 30 hours in Australian shrubland but there was no report of a road accident to help the search.
The expansion of the probe came as Jeremy Corbyn declared Carillion's demise a "watershed moment" that should end "rip-off privatisation".
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