BEIJING, Dec. 7 -- China Minmetals Corp., the nation's largest metals trader, continues to test the repaired concentrate pipeline at its Century zinc mine in northern Australia and can't say when output may restart.

Customers are still sourcing alternative supplies while the company seeks to complete testing on a bypass section to the pipeline that ruptured on Oct. 5, Sally Cox, a spokeswoman for Minmetals' Melbourne-based MMG unit, said today by phone. The bypass was connected last week, though it's unclear when production may restart, she said.

"We've completed the installation of the bypass, but we are just taking it slowly in terms of re-pressuring the line and undergoing some pretty thorough monitoring and testing prior to re-commissioning the line and restarting the plant," Cox said.

The mine in Queensland state is the world's second-largest open-pit zinc operation. Nyrstar NV, the world's largest smelter of zinc, buys concentrate from the mine, according to MMG.