Federal investigators were focusing Monday on a descent mechanism as the possible cause of the crash of a Virgin Galactic space vehicle in the Mojave Desert that killed one pilot and injured a second.

Investigators with the National Transportation Safety Board have been at the crash scene of SpaceShip Two in the Antelope Valley since Saturday along with its acting Chairman Christopher A. Hart, who is serving as the agency’s spokesman.

SpaceShipTwo crashed Friday morning minutes into a test flight, sending pieces scattered for miles in empty Mojave Desert scrub just east of Red Rock Canyon Park. Co-Pilot Michael Alsbury, 39, was killed in the crash while pilot Peter Siebold, 43, parachuted to safety but was injured.

Hart said at the Mojave Air & Space Port, where the flight originated, that the co-pilot might have prematurely released a lever unlocking a device that slows the spacecraft down after reaching sub-orbital altitude. Moments later the craft disintegrated.

However, Hart warned it was far too soon to conclude that pilot error was indeed the cause of the crash.

The crash marked a huge setback for billionaire Richard Branson, who founded the company in 2004 to carry passengers up to an altitude of 62 miles above the Earth. Branson was at the scene over the weekend as well.

On Monday, Branson spoke out on U.S. morning talk shows and reiterated his commitment to continue developing a commercial passenger space craft.

“It’s a grand program which has had a horrible setback, but I don’t think anybody watching this program would want us to abandon it at this stage,” he said, on the "Today" show.

Friday’s test flight was done with partner Scaled Composites, which designed the aircraft and was started by aviation pioneer Burt Rutan. It is now a subsidiary of Northrop Grumman Corp.

In January, the SpaceShipTwo completed its third successful rocket-powered test flight when it reached an altitude of 71,000 feet, the highest to date, and a speed of Mach 1.4. During that flight, the craft was powered by a rubber-based fuel.

During Saturday’s flight it was using a new plastic-based fuel, leading to some speculation about whether the fuel might have been a factor in the crash. However, Hart said FAA was a “long way” from finding the cause.

In May, Virgin Galactic reached an agreement with the FAA to set parameters on how the flights will take place in national airspace. About 700 people had signed up to fly on the six-passenger craft, which could have started flights as early as next year from New Mexico. Tickets cost roughly $250,000.

“I think this means that you are not seeing commercial flights next year and perhaps for another two or three years,” said Marco Caceres, senior analyst and director of space studies for aerospace research firm Teal Group.

The crash follows by three days the crash of another commercial spacecraft. An Orbital Sciences rocket carrying supplies to the International Space Station crashed seconds after liftoff in Virginia on Tuesday.

SpaceShipTwo took off with carrier aircraft WhiteKnightTwo at about 9 a.m. from the Mojave Air & Space Port in the Antelope Valley. Problems developed after the space vehicle was released and ignited its rocket engines.

The company first reported there was an “anomaly” with the flight six minutes after takeoff in a 10:14 a.m. tweet. The WhiteKnightTwo returned safely. The company said in a prepared statement at its website it would “work closely with the relevant authorities to determine the cause of the accident and provide updates as soon as we are able to do so.”

Virgin Galactic is by far the leader in commercial space operations. Its closest competitor is XCOR Aerospace, also at the Mojave Air & Space Port, which is developing a two-seat suborbital vehicle to take up a paying passengers and scientific experiments into near-space.

Technology entrepreneur Jeff Bezos, chief executive of Amazon.com Inc. and owner of the Washington Post, is developing a suborbital vehicle at his spaceflight startup, Blue Origin, in Kent, Wash. Caceres said he is much further behind.