Update 5:59 p.m.: The Shell icebreaker, Fennica, has cleared the St. Johns Bridge and has moved past the protestor blockade to continue on the Willamette River.
Reporter Amelia Templeton was at the scene as the ship crossed under the bridge. Protesters weighed down the nearby docks, yelling "Stop the boat!" as the Fennica moved by. Templeton said the ship appeared so close to the protestors paddling nearby that they could have reached out and touched it as it passed.
Update 5:29 p.m.: The Shell icebreaker, Fennica, is making its way down the Willamette River after undergoing repairs in Portland this week.
Kayakers paddled to the middle of the river as the icebreaker approached the St. Johns Bridge. Law enforcement quickly dispersed to remove the kayakers from the path of the ship. Greenpeace says that protestors in the water have effectively created a new blockade.
Update: 4:45 p.m.: So far, two Greenpeace protestors hanging from the St. Johns Bridge have been detained. Kayakers on the Willamette River are also being detained by the U.S. Coast Guard.
Update 4:05 p.m.: Officials said safety is the No. 1 priority in the effort to remove Greenpeace activists from the St. Johns Bridge. Currently Portland police, fire personnel and other emergency responders are at the scene.
"I don't think we've seen anything like this," said Portland Police Sgt. Pete Simpson. "Obviously this is a very unique situation for the city of Portland ... It is a complex operation when you consider all the government agencies (involved)."
Officials plan to hold another press conference following the conclusion of their operation.
Update: 3:40 p.m.: Law enforcement has ordered all traffic out of the Willamette River, which includes kayak protesters. OPB's Amelia Templeton reports that police are prepared to arrest people that remain in the water.
Update 3:30 p.m.: Greenpeace reports that law enforcement are moving to extract activists from the St. Johns Bridge. The protestors on the bridge have been escorted from the scene.
Updated 2:38 p.m.: ODOT announced that the St. Johns Bridge is closed in both directions for all travelers. Police are on the scene.
Updated 11:50 a.m.:Judge rules Greenpeace will be fined $2,500 an hour if protest blocking Shell ship continues. This story will be updated as more information becomes available.
Original post 10:23 a.m.: A Shell icebreaking vessel headed to an oil drilling site in the Arctic attempted to leave Portland Thursday but turned around and headed back to the dry dock after a brief standoff with protesters dangling from the St. Johns Bridge.
The U.S. Coast Guard escorted the icebreaker, named the Fennica, on the Willamette River and warned the activists that they were breaking the law.
Thirteen protesters used ropes to dangle from the bridge while more than a dozen others paddled below in kayaks. The stand-off went on for about 15 minutes before protesters watched as the Fennica turned around and headed back to the dock it came from.
"This is absolutely a victory. Basically we've stopped them," said Meredith Cocks, one of the protest organizers with Portland Rising Tide.
The Fennica has been in Portland for repairs since Saturday. It was originally scheduled to depart Wednesday morning. Federal regulators say Shell can't start drilling until an icebreaker is on site.
The Greenpeace activists took their positions in the wee hours of Wednesday morning. Organizers say they have enough supplies to remain suspended from the bridge for several days.