Three people have been killed and three others seriously hurt in an explosion at a rocket-testing site in the US state of California, officials say.
The blast at the Mojave Air and Space Port happened at a site run by space tourism pioneer Burt Rutan.
Mr Rutan said the incident happened during a test of the flow of nitrous oxide through an injector.
The gas is used to test rockets which Mr Rutan's company is developing to offer tourists a chance to visit space.
Two people were killed instantly and the third died later in hospital.
The explosion occurred at 1430 local time (2130 GMT) on Thursday.
Local TV broadcast pictures taken from a helicopter showing debris scattered across the area in the Mojave desert, north of Los Angeles.
Speaking to the Associated Press, Mr Rutan - who was not at the site at the time - described the incident as a "very big deal".
At a later news conference, Mr Rutan said officials did not yet know why the explosion occurred and added that nitrous oxide was not normally considered a hazardous material.
The site's general manager, Stuart Witt, said the area's activities were "inherently risky".
"These are not the days we look forward to but we deal with it," Mr Witt told AP.