According to Reuters, about 600 Fenoco transportation group employees went on strike earlier this month, demanding recognition of their labor union.

Output, primarily from Xstrata and Drummond mines, has been affected with 130,000 tonnes of coal prevented from being transported daily from the companies’ rail ports to Caribbean destinations.

"Fenoco canceled the meeting," union representative Felix Herrera told the news service.

"We don't know why and we don't know when it will be rescheduled. The strike continues."

Neither Drummond nor Xstrata have made public comment on the situation. In the meantime, Xstrata coal is being shipped by truck to the port.

Xstrata estimates total output of 11 million tonnes from its Prodeco operations, while Drummond is anticipating output of 27Mt, Reuters said.

The recent safety strike by more than 8000 Drummond workers ended after four days, but Sintramienergetica union representative Joaquin Romero said the group’s wishes for enhanced safety following the recent death of worker Dagoberto Clavijo – as well as for full benefits to be given to the dead miner’s family – were not heeded.

Clavijo was fatally injured in March at Drummond’s Pribbenow surface mine in the Cesar province of northern Colombia when the truck he was operating fell into the pit.