Copper production at Chilean copper mine Escondida, the world's largest copper mine, fell 30% on the year in the first quarter to 234,229 metric tons of copper, miner controller and operator BHP Billiton Ltd (BHP) said late Wednesday.

The drop in production was due to the combined effect of lower ore head grade, increased hardness of the ore treated which resulted in lower copper recovery, and production problems at one of the concentrator plants.

Escondida produced 155,956 tons of copper contained in concentrates and 78,273 tons of copper cathodes.

While concentrate production plummeted 45% on the year, cathode production increased 44% on the year due to "improved recovery and an increase in the level of activity and ore accumulation in the process stockpiles," the miner said.

BHP holds a 57.5% stake in Escondida, while Rio Tinto PLC (RTP) currently holds a 30% stake, which will drop to 15% once Aluminum Corp. of China Ltd. (ACH), or Chinalco, seals its tie-up with Rio Tinto and Chinalco takes the other 15%. A Japanese consortium made up of Mitsubishi Corp. (8058.TO) (60%), Mitsubishi Materials Corp. (5711.TO) (20%), and Nippon Mining & Metals Co. (JJD-MMM) (20%), hold a total 10% stake in Escondida, while International Finance Corp. (IFC.KW), the private sector unit of the World Bank, has the remaining 2.5% interest.

-By Carolina Pica, Dow Jones Newswires; 56-2-820-4244; carolina.pica@dowjones.com