BHP Group Ltd. said iron ore output in its first quarter rose 2% from the year before, as concerns grow that moves by major miners to ramp up production of the steel-making material may lead to over-supply.

BHP beat first-quarter iron ore output estimates on Thursday as the mining giant benefited from efforts to ease bottlenecks at its Western Australia operations, while copper production was lifted by better grades at its Escondida mine.

BHP sees growth in copper, iron ore, and steelmaking coal production, driven by higher grades and recoveries, amid China's potential stimulus measures.