A series of lockdowns in the country and South Gobi forced roster changes that saw personnel numbers below 25% of planned requirements, said the company.

Copper production fell as a result to 36,735 tonnes, a decrease of 19% compared to the first quarter. Gold production was 113,054 ounces, lower by 22%.

Mill throughput was also impacted by reduced personnel numbers due to COVID-19, falling 2% to 9.4 million tonnes in comparison to Q2 2020, and 4% lower than Q1 2021.

Underground development progress was also "significantly" impacted by the COVID-19 constraints on site and in Mongolia

"COVID-19 cases increased significantly in Mongolia during Q2 2021, causing a series of lockdowns in the country and South Gobi region which limited the ability of Oyu Tolgoi to maintain normal roster changes for its workers," said the company.

However, the company noted that as of July 9, that the workforce is 93% fully vaccinated and appropriate controls continue to be followed at site.