A search was underway Saturday for a woman who went missing after a raft flipped in Disaster Falls in Dinosaur National Monument/Kurt Repanshek file photo of Disaster Falls at low water around 850 cfs.

Editor's note: This updates with the search ongoing for a woman who went missing when a commercial raft flipped in Upper Disaster Falls on the Green River in Dinosaur National Monument. Provides additional details.

A day-long search for a woman who went missing after a commercial raft flipped on the Green River in Dinosaur National Monument proved fruitless as sundown neared Saturday, as crews were able to recover the raft that had been pinned upside down against a rock but were unable to locate the woman's body.

The raft, an oar boat owned by Adrift Adventures, flipped in the Upper Disaster Falls rapid around 5 p.m. Friday.  An unspecified number of occupants made it to the shore, but a 63-year-old female was unaccounted for, a park release said. The raft was pinned to a rock in the river due to the force of the current. The group's trip leader -- there were 19 passengers and five guides in the party -- notified the monument about the incident by satellite phone.

Members of the rafting group searched the shoreline for the missing rafter. They later were aided by a helicopter dispatched by Classic Lifeguard Air Ambulance, which searched the river corridor until darkness Friday. 

A larger search-and-rescue team was mobilized at Gates of Lodore at the monument's river launch site Saturday morning and floated the seven miles through the Canyon of the Lodore down to the rapid to aid in the effort. The crew, which arrived at the site about 10:30 a..m., was able to free the pinned raft, but there was no sign of the missing rafter.

Other members of the group continued down river, en route to Echo Park where they would leave the river, according to a park spokesman.

The search-and-rescue team consisted of three rafts with two Moffat County (Colorado) staff, four Dinosaur National Monument rangers and one commercial guide from Dinosaur River Expeditions, another commercial outfit permitted to run the river. High river flows in the area were complicating search efforts by creating hazardous conditions for the search-and-rescue team.

Disaster Falls, which has a class III-IV rating depending on river levels according to the International Scale of River Difficulty, is located in a remote section of the Canyon of Lodore. The Green River was flowing at approximately 8,600 cubic feet per second at the time of the incident.

The rapid was named by Major John Wesley Powell during his 1869 expedition down the Green and Colorado rivers. One of the boats in his party capsized in the rapid and was "dashed to pieces."

River runners float the river either in oar boats, in which a guide uses oars to steer the raft while passengers ride, or paddle boats, in which guide and passengers use paddles to propel and steer the raft.