The early stages of a search are under way in the Flathead Valley area for a missing aircraft that was carrying two Daily Inter Lake staff writers and two men from Missoula.

The blue-and-white, single-engine airplane with a low wing took off from Kalispell City Airport just after 1:30 p.m. Sunday. It was rented by Sonny Kless of Missoula from North Star Aviation and it has not been returned to the Missoula airport.

On board were Melissa Weaver, 23, a police and courts reporter with the Inter Lake, and Erika Hoefer, 27, a business reporter who also writes for the Flathead Business Journal. The second man on board has yet to be identified.

Weaver's car was still at the city airport on Monday morning and the two were supposed to be at a barbecue with friends at 6 p.m. Sunday.

Their absence and lack of phone contact was considered strange by Weaver's roommate, prompting her to contact the Flathead County Sheriff's Office and other agencies Monday morning.

Sgt. Ernie Freebury organized an initial search, with a state airplane checking on prominent wilderness airstrips just after noon.

By 2 p.m., several private aircraft with the Montana Civil Air Patrol were involved in the search, along with a U.S. Customs Service helicopter that was detailed to the Western Governors conference in Whitefish. Glacier National Park officials and the Montana Aeronautics Division also are engaged in the search.

Freebury said radar data from Salt Lake City was being analyzed along with cell-phone tower information.

He said Hoefer last updated her Facebook page at 1:40 p.m. and the last text or voice message from any of the individuals' phones occurred at 1:51 p.m.

Kless last made radio contact with the tower at Glacier Park International Airport at 2:11 p.m., reporting that he was east of Kalispell, traveling south to north.

It was unclear whether any type of flight plan had been left at any airport, and the group was reportedly on a scenic flight.

Freebury said the search area currently is very broad, but it will be narrowed.

He said the type of plane involved was carrying an older-style transponder.

Weaver, a University of Montana graduate from Billings, and Hoefer, from Beloit, Wis., began work at the Inter Lake in December 2009.