(Updates with details of plane, flight origin, two victims)
By Dana Feldman
SANTA MONICA, Calif., Sept 30 (Reuters) - The fiery crash-landing of a small jet en route from Idaho's Sun Valley resort area to the Santa Monica airport near Los Angeles killed everyone on board, though the number of victims has yet to be determined, authorities said on Monday.
The twin-engine Cessna Citation 525A swerved off the right side of the runway on landing at Santa Monica Municipal Airport at about 6:20 p.m. on Sunday, slammed into a hangar and burst into flames, airport manager Stelios Makrides said.
The hangar collapsed around the plane, and investigators have not been able to reach the aircraft to determine how many people were on board, Makrides said. He said it was not known whether anyone was inside the hangar just before the crash.
Santa Monica-based construction firm Morley Builders said in a statement that its chief executive officer, Mark Benjamin, and his son, Luke Benjamin, a senior project engineer with the company, were among those on the plane and presumed dead.
The plane had departed on Sunday evening from Friedman Memorial Airport outside the mountain town of Hailey, south of the world-class ski resort of Sun Valley in south-central Idaho, officials said.
The Cessna Citation family of jets has a seating capacity of five to nine people, and the model that crashed is believed to have seating for a pilot, co-pilot and six passengers.
An investigation team from the National Transportation Safety Board arrived at the scene on Sunday night, NTSB spokesman Keith Holloway said. Makrides said the NTSB returned to the crash site on Monday morning to resume its probe.
Captain John Nevandro of the Santa Monica Fire Department said it was "an unsurvivable crash." Makrides and Holloway said there were no signs of survivors.
Makrides said something occurred as the plane touched down that made it veer to the right, but that the precise cause of the accident was under investigation.
Witness Charles Thomson told local television station and CNN affiliate KCAL-TV that a tire on the plane's landing gear appeared to burst as it touched down.
"It wasn't an emergency landing," Thomson said. "It was just a landing, and the tire popped afterwards."
News pictures taken shortly after the crash showed billowing black smoke curling up over aircraft at the airport, which serves communities west of downtown Los Angeles. Subsequent images showed the tail of an aircraft protruding from the partly collapsed hangar, flanked by fire trucks. (Writing and additional reporting by Steve Gorman; Laura Zuckerman from Salmon, Idaho, also contributed to this report; Editing by Cynthia Johnston, Leslie Adler and Cynthia Osterman)