1.   Driver error, or mechanical fault?

2.   Police believe it was a mechanical fault.

3.   At the same time, no one has found any clear evidence of mechanical fault, though investigators are studying several possible scenarios.

4.   For example, the persistent lack of distinctive microscopic signs of a bomb blast, some board experts say, bolsters the case for a mechanical fault.

5.   Other kinds of tiny fissures and cracks can also help pinpoint a mechanical fault, investigators say.

6.   Riding the trial circuit, Penny and Hope hook up with Ransome Barlow, a hardbitten trainer whose handling of his dog Bute is perfect to a mechanical fault.

7.   A mechanical fault during the routine exercise sent the jet plummeting to earth over the weekend near the northern village of Shiroro, the independent Concord newspaper reported.

8.   Army pilot Latif Derikvand said that mechanical fault was the likely cause of the crash.

9.   But investigators found no trace of any mechanical faults that could have caused him to veer off the motorway and hurtle down an embankment.

10.   But there was no immediate evidence of sabotage, and the cause was likely a mechanical fault, said Perera.