The upgrade brings the port up to revised environmental regulations.

The government closed the port in January as a consequence of the new law, which bans the use of cranes and barges to load boats.

As a result of the closure, Colombia’s coal exports dropped by a third and Drummond had to declare force majeure as it was unable to use any other port to ship the fuel.

Coal miners in Colombia previously warned that new regulations and delays in environmental approvals had begun to affect production and caused further damage to the local mining industry.

Production of the world's fourth largest coal exporting nation dropped 4% to 85.5 million tonnes last year, falling short of its 89Mt target.

Coal shipments account for 12% of the Colombia's total exports, second to oil, which makes up 40%.