A police probe has been launched after a crane was deliberately set on fire at the site of the £350 million Aberdeen Harbour development.
Two appliances from the Scottish Fire and Rescue Service (SFRS) were sent to the scene, with reports first saying waste materials had been set alight.
However, when the 10 firefighters arrived on scene, they were met with the crane ablaze.
Police Scotland has also launched an inquiry into the circumstances surrounding the blaze.
And those behind the harbour expansion project say security at the site has now been increased.
Pictures of the aftermath have shown the cab of the crane fully destroyed, with smoke damage affecting other parts of the structure.
A spokeswoman for the Harbour development said: “The Aberdeen Harbour Expansion Project at Nigg Bay was subject to an episode of serious vandalism which took place on the evening of December 26. A full police inquiry is under way.
“Security has been stepped up on the site as a result of the incident, which will have no impact on the working schedule.”
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A spokeswoman for the Scottish Fire and Rescue Service said Police Scotland was requested on scene when it became clear that the fire had been set deliberately.
She said: “Two appliances, both from Altens fire station attended the construction site near the harbour in Aberdeen, using one hose reel jet and portable lighting to extinguish the fire.
“At first, it was reported that a quantity of waste material was on fire, however, it was discovered that a mobile crane was also ablaze.
“The police were requested to attend, as it was suspected that the fireraising was wilful.”
Detective constable Wilma Ritchie said: “Officers are appealing for witnesses following a wilful fireraising to a crane and vandalism to a number of vehicles at the Aberdeen Harbour Expansion Project at Greyhope Road.
“The incident is understood to have happened between around 6pm and 7pm on December 26. Anyone with information or who saw anything suspicious in the area between the times given is urged to contact police on 101 using reference number CF0318061218.”
The £350m redevelopment at the Bay of Nigg is expected to open to cruise ships in 2020.