NEW YORK — First Nickel Inc.’s Lockerby nickel mine in Sudbury, Ontario, will produce less nickel and copper than previously expected due to unplanned rehabilitation work and slower-than-expected ore source development, the company said.

Both issues have since been resolved, First Nickel said.

The company’s fourth-quarter nickel production is expected to reach 1.3 million pounds, down from a previous estimate of 2.1 million to 2.5 million pounds. Meanwhile, copper production will reach 1 million pounds, down from previous guidance of 1.4 million to 1.6 million pounds.

It expects 2012 nickel output will reach 5.7 million pounds, down from a previous estimate of 6.3 million to 7.4 million pounds, and projects copper output will reach 4.5 million pounds, the low end of a previous estimate of 4.5 million to 5 million pounds.

In addition, about 60,000 tonnes of ore from the mine processed by Xstrata Nickel’s Strathcona facility saw lower-than-expected ore grades and recovery, reducing nickel production by 460,000 pounds.

“An investigation into both the lower-than-predicted ore grade and lower-than-plan(ned) recovery is in progress,” the company said, adding that “both ore grades and metal recoveries for lots processed prior to the fourth quarter performed within an acceptable variance range.”

The Toronto-based company now expects Lockerby to achieve full production in the first quarter of 2013.