BHP Billiton has halted output at its Olympic Dam uranium, copper and gold mine in South Australia after a haulage system suffered a mechanical failure.

It is not yet known why the automated system, in the Clark Shaft, broke and BHP says it is conducting a full investigation into the incident.

The unmanned shaft supplies ore from underground to the surface processing facilities and is backed up by a secondary haulage system that still works.

A BHP Billiton spokesperson told AdelaideNow that the haulage system is blocking the mine, and that operations have stopped to ensure the safety of staff.

No one was injured in the incident.