Searchers say they've detected a faint signal from a locating beacon they think may be coming from a missing plane piloted by a Twin Cities man and carrying three of his children.
Luke Bucklin's plane went missing in western Wyoming Monday, shortly after he took off from Jackson Hole in a snowstorm.
View a map showing where the plane went missing.
Officials have narrowed their search to a 9 square mile area east of Gannett Peak, the highest peak in Wyoming at just over 13,800 feet.
Sgt. Ryan Lee, a spokesman for the Fremont County Sheriff's Office, said ground crews in the area have hand-held devices that can assist in pinpoint the radio signal as it bounces off rocks, cliffs and peaks.
"Which are predominant in the area, and make the signal very difficult to pinpoint," Lee said.
Lee said the signal is automatic, so it isn't an indication of what condition the plane or its passengers might be in. He said the beacon is battery powered, but could continue to signal for weeks under the right conditions.
Lee said officials believe the signal is coming from the missing plane because no other aircraft have been reported missing in the area.
Crews of mountaineers, many of them associated with the National Outdoor Leadership School in Lander, have been shuttling in and out of the area by helicopter to search on the ground in deep snow and frigid temperatures. Three helicopters, including one from the U.S. Air Force base in Cheyenne, and other aircraft continue to search from overhead.
On Thursday, a plane equipped with sensitive gear flew the area to try to detect a signal from the missing plane's locater beacon. Such signals may either be triggered manually, or on impact in the manner of an air bag on a car in a crash.
Another snow storm is scheduled to move into the area over the weekend. Officials said Thursday that they still regard the search as a rescue mission, not merely a recovery effort.
Bonnie Harris, a family friend of Luke Bucklin and his wife, Ginger Bucklin, said the family had been in Wyoming for a wedding and family vacation. Ginger Bucklin and the couple's youngest son flew home separately on a commercial flight, Harris said.
Luke Bucklin is president and co-founder of the Bloomington, Minn.-based Web development company Sierra Bravo Corp.
(The Associated Press contributed to this report.)