Searchers in Wyoming added two fixed-wing aircraft to three teams of mountaineers Saturday as they continued the search for four members of a south Minneapolis family whose single-engine plane disappeared amid rugged terrain Monday.

No physical evidence of the plane has been found, though searchers continue to hear the ping of an emergency transponder that they think may be coming from the plane that was piloted by Luke Bucklin, 40. His sons, 14-year-old twins Nate and Nick, and 12-year-old Noah, were also in the plane when it disappeared. They were returning from Jackson Hole to the Twin Cities.

The search is at an elevation of 11,000 to 12,000 feet near Wyoming's highest peak in an unforgiving landscape of canyons, gullies, timber and boulder fields. Ernie Over, public information officer for the rescue operation coordinated through the Fremont County Sheriff's Office, said the terrain is making it difficult to locate the transponder.

Climbers in the 9-mile-square area have handheld signal detectors and they hear the signal "in almost every canyon they search," he said.

"We have been unable to pinpoint the source," Over said. "It's an incredibly rocky terrain and landscape, and there is so much shadowing and echoing going on. But they're still up there looking."

Batteries on such transponders usually last about two weeks, he said.

Three helicopters were joined Saturday by two Civil Air Patrol fixed-wing aircraft to try to narrow the location of the transponder signal. One copter was searching the area visually in grids, looking for anything unusual.

Though the weather was good when the search resumed Saturday morning, the wind had picked up by late afternoon, and snow flurries were expected.

Over said the search will resume Sunday, when the wind is expected to pick up again and there will be snow showers. Over said the effort is still considered a rescue operation.

In the Twin Cities, the Bucklins' minister, Pastor John Sommerville of City Church in Minneapolis, said relatives were "doing as well as can be expected." They include Luke Bucklin's wife, Ginger, and his son, Oliver, 5. The two had been in Wyoming with the rest of the family but returned to the Twin Cities. "They are continuing to be hopeful, but realistic at the same time," Sommerville said. "The resources the search and rescue people are devoting to this is giving them comfort."

He said family members feel "overwhelming support" from their friends, community and church. Friends of the missing boys started a "Wear Blue for the Bucklins" Facebook page that has drawn 2,200 fans, and hundreds of people have joined a Web page called

Luke Bucklin, 40, is president and cofounder of Sierra Bravo, a Web development company based in Bloomington.

Mary Jane Smetanka • 612-673-7380