Updated

A search for a missing Idaho pilot believed to have gone down in southern Oregon is expanding to include both private help and assistance from neighboring Oregon counties and a California county, a sheriff said.

The family of Tony Nicholls, 48, of Meridian, Idaho, has set up a Facebook page to help coordinate private resources like searchers on all-terrain vehicles, said Sheriff Tim Evinger of Klamath County, Ore.

Siskiyou County, Calif., as well as Curry and Josephine counties in Oregon are providing search assistance as well, Evinger added Tuesday night.

Nicholls dropped off his two stepsons in Lakeview, Ore., on Thursday and was to return home that day because his daughter was graduating from high school over the weekend.

Klamath County officials have said radar and cellphone records indicate the last known location for the 1978 Grumman "Cheetah" aircraft was near Hart Lake in the area of Plush, Ore.

Still, the search area is vast, reaching into Nevada and California and encompassing some 4,000 square miles of mountains, forest and high desert.

Tuesday's air and ground search yielded "a couple of false alarms" but no aircraft, Evinger said.

Search coordinators are reaching out for all resources, both public and private, as investigators sort through clues and "attempt to find the best place to use these resources in thousands of square miles of search area," he said.

Amy Nicholls told the Idaho Statesman (http://bit.ly/KCKCRQ) Tuesday that her husband is a marathon runner with a high pain tolerance and called him "the toughest man I've ever met in my life."

She says she had exchanged text messages with him during his return flight and his last message said he had "cleared the mountains."

"I don't know what he cleared," she said.

Evinger said searchers had identified high-priority spots from cellphone and flight tracking data, but it's still a "needle in a haystack" search.

Besides rough terrain, there are stands of Ponderosa pine 100 feet tall that could conceal an aircraft on the ground.

"There's also been snowfall, and the plane is white," he said.

Searchers have set up a tip line at (541) 883-5130, extension 603.