BHP Billiton Ltd. (BHP.AU) said Thursday it continues to mine ore underground at its Olympic Dam operation in South Australia after the breakdown of the mine's main haulage system.

BHP said the fully automated Clark shaft at the mine broke down on Tuesday night, but gave no further details of the incident.

"In the meantime underground mining is continuing with ore being hoisted to the surface via the secondary Whenan shaft," BHP said.

BHP said it is currently examining what impact the temporary closure of the main shaft for hauling ore at the mine will have on production, planning schedules and budget.

"This work is expected to be completed in the course of the next two weeks and will run in parallel with both the government and company investigations into the incident," BHP said.

-By Alex Wilson, Dow Jones Newswires; 61-3-9292-2094; alex.wilson@dowjones.com