Cromarty Firth rig dust cloud 'posed little or no risk'
A dust cloud seen at an oil rig which was later occupied by Greenpeace "posed little or no risk to the environment", a port authority has said.
The Cromarty Firth Port Authority said the dust came from a supply ship as cement was being loaded to the rig.
The cement powder was considered to have posed little or no risk "under offshore chemical regulations".
The cloud was spotted on 8 June, the day before Greenpeace campaigners boarded the rig in a protest.
Local environmental group Cromarty Rising raised concerns about the dust, saying that the cement powder could harm wildlife.
The Transocean rig was parked in the Cromarty Firth near Invergordon.
Greenpeace occupied it in a protest about the drilling of new wells. Its protest has continued with attempts to disrupt work to the rig out into the North Sea.
In a statement to BBC Radio Scotland, the Cromarty Firth Port Authority said the operators of the rig had sought guidance on weather conditions and wind direction before the cement was loaded.
Cromarty Rising said the cloud was released inside a Special Area of Conservation in the firth.
It said it will be raising its concerns with the Health and Safety Executive and authorities responsible for European protected species licensing.