California's Division of Occupational Safety and Health Administration (Cal/OSHA) has cited a private spaceflight company, Scaled Composites, in connection with an explosion that killed three of the firm's workers last July.

The citations faulted the Mojave, Calif.-based company for failing to provide "effective information and training of the health and physical hazards associated with nitrous oxide," a compound used during a July 26 test that ended in an explosion, killing three employees and injuring three others at the Mojave Air and Space Port, according to a report on

Scaled Composites built and flew the piloted, air-launched SpaceShipOne suborbital spacecraft three times in 2004, winning a $10 million Ansari X Prize in the process.

The firm was conducting tests as part of the development for SpaceShipTwo, a larger spaceliner designed to carry space tourists to suborbital space for Virgin Galactic, when the deadly accident occurred last summer. According to Cal/OSHA, Scaled Composites faces up to $25,310 in fines for three citations.

SpaceShipTwo, which like its predecessor will be air-launched by a carrier craft, is expected to carry up to eight people — two pilots and six passengers — at a time to an altitude of 68 miles (110 kilometers), where they would experience several minutes of weightlessness before returning to Earth.

Scaled Composites and Virgin Galactic officials were working toward a planned rollout of SpaceShipTwo later this year and operational flights in 2009 when the accident occurred.