Brazilian mining giant Vale SA produced slightly less iron ore than expected last quarter because of teething problems at a new plant in a fresh blow to an already tight global market for the steelmaking ingredient.

The world’s second-largest iron producer churned out 75.7 million metric tons in the second quarter compared with the 78 million-ton average estimate among analysts tracked by Bloomberg. The result was still up from both the previous three months and the Covid-impacted year-ago period.

Vale’s ongoing recovery from an early-2019 dam disaster makes it a major swing factor in a market in which demand remains strong despite China’s efforts to curb emissions and contain commodity inflation. Vale’s ability and willingness to expand and take back the No. 1 producer title it lost to Rio Tinto Group will help determine whether the market moves back into surplus. Rio Tinto has said suppliers are struggling to meet demand.

While Vale is resolving a rail interruption at one of its complexes in southern Brazil, production was held back by disruptions cause by the installation of a crusher plant at its S11D complex in the country’s north. The Rio de Janeiro-based also said it had pushed back resumption dates at other operations due to slower-than-expected permitting and extra work to increase dam safety.

Vale’s ramp-up took a hit in early June when it was ordered to restrict operations at its Timbopeba complex amid concerns surrounding the stability of another dam. In the first quarter, the partial resumption of Timbopeba had helped push up Vale’s output.

Still, Timbopeba delivered a better performance thanks to the commissioning of the three additional wet-processing lines in March. The company said a driver-less train solution at the complex is performing well.

In Monday’s production report, Vale maintained its full-year guidance of 315 million to 335 million tons and said it achieved annual output capacity of 330 million tons. The company expects to reach 350 million tons capacity by year-end and 400 million tons by the end of 2022.

Still, quarterly iron ore sales lagged output, coming in at 67.2 million tons. Rio Tinto said last week that its shipments fell 2% on the previous quarter and flagged annual exports could come in at the low end of its forecast, partly because of rainier-than-normal weather. BHP Group reported a 12% increase in quarterly shipments.

Vale is also one of the world’s largest nickel producers and a major copper supplier. Production of both metals fell in the second quarter and Vale said it’s reviewing annual guidance amid a strike at one of its complexes in Canada.

The Brazilian miner is set to release earnings on July 28.