Fire crews used ultra high-pressure lances to punch through thick walls of steel in a bid to extinguish a six-day blaze at a silo in Invergordon.
The silo, containing more than 14,000 tonnes of wooden pellets, caught fire at the Balcas plant in the Cromarty Firth Industrial Estate last week.
It is one of the first times crews have used the recently-introduced lances on the frontline to protect communities.
The incident began last Monday night and due to the unusual circumstances with wood fuel being alight and contained in the silo, crews did not leave the scene until Saturday morning.
Retained firefighters from Foyers used the lance to safely bore a hole through the 20mm steel wall of the silo – injecting water straight into burning embers buried under tonnes of material and halting the spread of the fire.
Fire engines and an aerial appliance were sent to the scene when the alarm was raised at 10.50pm last Monday.
Crews and site staff worked to empty the silo to dampen down remaining hotspots.
Area manager Rab Middlemiss, the local senior officer for the Highland area, said it was a challenging incident due to the large quantity of flammable material involved.
He added: “The fire was brought under control quickly in the early stages of the incident, and our crews were able to prevent any further damage to nearby buildings.
“The use of proven UHPL (ultra high pressure lances) technology was instrumental in allowing crews to safely get to fire and large hotspots that were otherwise completely inaccessible – eliminating the need for crews to dig through burning materials to reach the smouldering pellets and preventing further fire spread.”
Ultra high pressure lances were recently introduced following a £7.6 million investment in Scotland’s retained firefighters.
A spokeswoman for Balcas said: “Balcas are enormously grateful to Invergordon and other local fire services. Their professionalism and attitude is matter of great admiration for all of our team.
“The generating plant and production facilities have returned to normal service.
“An investigation into the cause is underway. It will be some time before we know the outcome of this.
“With additional pellet storage capacity on site, production can recommence and this incident should not impact any current customer orders.”