A helicopter crashed in foggy weather off the Oregon coast Sunday, killing two men and a woman who were retracing the path of Meriwether Lewis and William Clark.

The helicopter was one of two choppers that had been flying in tandem as part of the Flight of Discovery project, in which a team of volunteers fly the river corridors and overland routes of the Lewis and Clark expedition, group member Wendi Goldsmith said.

The pilot of the other helicopter called the Coast Guard, saying he had lost communications with the downed chopper, Coast Guard Lt. Brooks Crawford said. The weather was foggy with visibility of about a half mile, he said.

The helicopter was a Robinson R44, a small craft able to carry three or four people, Crawford said. It left Vancouver, Wash., early Sunday and headed toward the ocean.

John Overholser, who owns a refueling station in Astoria, said the pilot of the surviving helicopter went back in an attempt to find the victims.

"Two life jackets and an oil slick is they saw when they went back out," he told KATU-TV in Portland.

Coast Guard crews recovered the bodies. The identities of the victims, who were from Southern California, were being withheld until relatives were notified, Crawford said.

About 40 members of the group — comprised of scientists, historians, videographers and pilots — were in Oregon this weekend, Goldsmith said.

The group previously traveled the trail to Oregon. This summer, they planned to retrace the return route to Missouri and teach students about geology, history and the explorers along the way.

"All of us are very much shaken, upset and just shocked," Goldsmith said. "But there are some us who feel like it would be the wishes of the deceased to push on and culminate the last leg of a process that has lasted four years."