Environmental campaign group Greenpeace says 13 of its activists have blocked Shell's Polar Pioneer drilling rig as it tries to leave Seattle for Arctic waters.
Six climbers who boarded an oil rig in the Pacific have now left after worsening weather conditions caused them to halt their activities.
Last week the group had scaled the Transocean-owned rig, which they claim is being sent to the Arctic by Shell.
The oil giant, which announced plans to by BG Group earlier this month, had been seeking an injunction from a US federal court in Alaska to remove the six from the Polar Pioneer.
Danish toy giant Lego has decided not to renew its commercial relationship with oil giant Shell following a targeted campaign by Greenpeace about its Arctic drilling plans.