(Reuters] -Miner Barrick Gold, (NYSE:) said Thursday that first-quarter production was down 17.7% compared with the prior three months. The decline in output at its Carlin or Cortez mines caused by lower output.

Barrick claimed that the lower gold output resulted from a mechanical failure at Carlin, Cortez and Cortez mining operations and an insufficient supply of underground higher-grade ore.

Company is due to publish its quarter-end results May 4.

The shares that are U.S. listed were up nearly 31% this year. However, they fell 0.9% in premarket trades.

Barrick indicated that the company expects its all-in sustain costs (AISC), for gold, which is a critical industry indicator, to increase by 19% to 21% over the fourth quarter.

Preliminary gold production by the miner was 990 million ounces for the three-months ended March 31st, compared to 1.20 million in the fourth quarter.