Drummond issued a statement to employees this week announcing it was slashing the normal 24-hour operation by three-quarters as of Thursday. It has also asked the government for permission to suspend some labour contracts, Reuters reports.

"Although the company keeps maximum levels of inventory at train-loading stations, at the mine and at the port yards of 3 million tonnes, the current levels are higher than 4.7 million tonnes," Drummond said.

"Inventories at load stations are at peak levels and cannot receive more coal from mining operations. Additionally, we have more than 1 million tonnes in inventory at the pits that cannot be transported to loading stations."

Drummond is Colombia’s second-largest coal exporter and had a loading suspension issued for its port by the Colombian government after the near-sinking of one of its loaded barges.

The suspension has been in action since February 6 and is preventing the company from exporting.

Colombia’s largest coal exporter, Cerrejon, has also been inactive since the beginning of the month due to employee strike action. The company declared a force majeure this week.