Brazilian mining company Vale SA has resumed operations at its Carborough Downs coal mine, effectively lifting a declaration of force majeure, after a carbon monoxide leak forced the miner to suspend the operations of the mine on May 31 thgis year.

No employees were adversely affected and no environmental damage occurred at the metallurgical coal mine following the detection of abnormal levels of carbon monoxide, Vale said in a statement.

"Carborough Downs has resumed production at a safe rate," the Rio de Janeiro-based company said in a securities filing on Monday. "Output will gradually normalize as the remaining operational and geological issues are resolved."

The mine, located in the Central Bowen Basin of Queensland, Australia, churned 82,000 metric tonnes of coking coal, used in steel production, in the second quarter of 2012, Vale said. This pales in comparison to the 325,000 metric tonnes produced in the first quarter.

A force majeure grants a company to suspend contractual obligations in the face of unexpected and drastic occurrences such as war or natural disasters. It is a legal clause that allows companies to miss deliveries.

Vale's total second quarter coal output, including metallurgical and thermal coal used in power stations, reached 2.5 million metric tonnes, 1.11 million metric tonnes of which were from the giant Moatize mine in Mozambique.