Chilean copper exports rose last month despite lower prices, signaling mines in the world’s top supplier of the metal are recovering from operational setbacks that dragged down production.

July shipments were up 1.5% versus June and 31% from a year earlier, according to data released by the central bank Wednesday. While mining and shipping schedules help explain monthly swings, July’s result indicates recovering output given average prices were higher the month before. 

Chile, which accounts for more than a quarter of the world’s mined copper, had seen production slide to the lowest levels in 20 years as companies including state-owned Codelco grapple with low ore quality and operational problems. Massive investments to tap richer ore should see output start to increase this year, according to government estimates.