It is understood the fire sparked through the natural drying-out process for the fuel, which was contained in a 30-metre-high industrial coal bin.
A spokeswoman for the cement firm explained that if stored for long periods and then moved, coal can start to heat.
She said: "We can confirm that the situation was fully under control at all times as the coal was methodically brought out and doused, and the fire service left site before 4pm after a discussion with the works operations manager.
"There was no disruption to the kiln during this time."
