By Ed Ballard

Glencore PLC (GLEN.LN) reported a year-on-year drop in first-quarter copper production on Tuesday, partly due to a planned shutdown for maintenance at its Collahuasi mine in Chile.

The Switzerland-based commodities giant reported a 9% decline in copper production from its own sources to 350,700 metric tons in the first three months of the year.

Glencore said the decline also reflected lower grades at the Alumbrera and Antamina mines due to mine sequencing.

Own-sourced zinc production of 356,200 tons was up 16% on the year. Nickel production was up 7% at 23,800 tons. Attributable ferrochrome production was up 15% at 385,000 tons.

Own-sourced coal production was 35.6 million tons, 4% up on the year. Glencore produced 2.6 million barrels of oil, a 52% increase on the year reflecting higher production from Chad.

Write to Ed Ballard at ed.ballard@wsj.com

Subscribe to WSJ: http://online.wsj.com?mod=djnwires