OGV Energy have been advised that a helicopter has landed on the rig this afternoon and several police have boarded the Paul B Lloyd Transocean asset and plan to remove the Greenpeace activists.
It was also reported that the activists have been placing themselves in danger by hanging from ropes.
There is onshore activity with a police van, car and a CCTV unit currently in place at Invergordon.
The first two Greenpeace activists climbed on to the rig on Sunday evening, calling for BP to end drilling for new oil wells.
Greenpeace said the 27,000-tonne rig owned by Transocean was on its way to the Vorlich field to drill new oil wells operated by BP.