An explosion at a rocket test pad at the Mojave Air and Space Port in Mojave, California, killed three people and critically injured three others Thursday. The explosion is said to have resulted from a test involving nitrous oxide flowing through fuel injectors during a check of a new rocket motor for SpaceShipTwo, a spacecraft being built for Virgin Galactic, a space tourism company.

Scaled Composites, an aerospace development company founded by Burt Rutan, the aerospace engineer who designed the first repeat sub-orbital space flight with his SpaceShipOne, employed the six. Rutan, who was not at the site at the time of the accident, said they were performing a test that was considered to be completely safe and had been done numerous times with SpaceShipOne.

Killed in the accident were Eric Blackwell, 38, of Randsburg, California; Charles May, 45, of Mojave; and Todd Ivens, 33, of Tehachapi, California.

"Our thoughts and prayers go out to the families and friends of those affected by this unfortunate event," said EAA Public Relations Specialist Dick Knapinski.

SpaceShipTwo is a small carbon fiber craft designed to carry seven passengers up to 65 miles above the earth, moving at speeds in excess of 12,000 mph. The spacecraft is based on technology used in SpaceShipOne.

EAA President Tom Poberezny has contacted Dick Rutan, brother of Burt Rutan, expressing his condolences and support on behalf of EAA.