Chile just registered its worst month for copper production since February as the world’s biggest supplier of the metal was hit with labor disruptions and poor quality ore.

September’s output was down 6.9% from a year earlier and 3.4% from August, according to data released Friday by the country’s bureau of statistics. 

The result—from a country that accounts for more than a quarter of the world’s mined copper—offers little relief for a tight market characterized by low stockpiles. Some mines are still catching up on earthworks and maintenance that was postponed last year in a bid to maintain production in the pandemic with reduced staffing.

Still, given part of the decline was due to labor strikes that were fairly quickly resolved, the implication is that production will bounce back in October.