The truck's tray was fully loaded at the time and the tray was partially raised during the incident.

The Queensland Mines Inspectorate said the rear dump truck had been incorrectly loaded with the load too far forward.

"A hoist cylinder hose failed whilst the load was being dumped," it said.

"The truck sustained damage to the hoist circuit hydraulic hoses prior to the event. Damage had not been reported or rectified."

The inspectorate said site procedures for dealing with hydraulics that would not lift an overload had not been followed.