Updated at 6:05 pm with information from a post-accident press conference.

DURHAM, N.C. — Virgin Galactic’s SpaceShipTwo suborbital spaceplane was destroyed Oct. 31 during its first rocket-powered test flight in nearly nine months, killing one pilot and injuring another.

At a 5 pm EDT press conference at the Mojave Air and Space Port in California, company officials and first responders said SpaceShipTwo suffered an “inflight anomaly” shortly after being released from its WhiteKnightTwo carrier aircraft and igniting its hybrid rocket engine.

“We do know one of the crew members was met by emergency responders, treated on the scene, and transported to Antelope Valley Hospital,” Stu Witt, chief executive of Mojave Air and Space Port, said at the press conference. “We also know that we have one fatality.”

Officials have yet to release the names of either pilot. The condition of the surviving pilot was not been disclosed, but Don Youngblood, Kern County sheriff, said that pilot was suffering from “major” injuries. Both pilots were employees of Scaled Composites, the company that developed SpaceShipTwo for Virgin Galactic, company president Kevin Mickey said.

SpaceShipTwo, attached to WhiteKnightTwo, took off from Mojave Air and Space Port at 12:20 pm EDT, according to Witt. Fifty minutes later, SpaceShipTwo separated from WhiteKnightTwo. Witt said that he “became aware of an inflight anomaly” two minutes later. The crash site, he said, was about 40 kilometers north of the airport.

Witt said he saw nothing unusual during the test that would lead him to conclude there was a problem. “I detected nothing that appeared abnormal,” he said. “It wasn’t because something did happen, it was what I was not hearing and not seeing. If there was a huge explosion, I didn’t see it.”

At the press conference, Mickey confirmed that the flight was the first to use a new hybrid rocket motor. Previous powered test flights, most recently on Jan. 10, featured a motor that used hydroxyl-terminated polybutadiene, a form of rubber. In May, Virgin Galactic announced it was switching the motor to a polyamide-based plastic.

At the International Symposium for Personal and Commercial Spaceflight in Las Cruces, New Mexico, on Oct. 15, Virgin Galactic chief executive George Whitesides said the company had completed a series of qualification tests of the new motor on the ground. “We expect to get back into powered test flight quite soon,” he said.

In an Oct. 31 statement, Sierra Nevada Corp. (SNC), which developed the original rubber-based hybrid motor, confirmed its motor was not used on this flight. “SNC had no involvement in the build or qualification testing of the motor used in this flight, nor in the integration of this motor to [SpaceShipTwo],” it stated. “We were not aware of the test today, nor present on site or remotely monitoring the testing in Mojave, California.”

The National Transportation Safety Board (NTSB) announced Oct. 31 that it was assembling a “go-team” to travel to Mojave to investigate the accident. Mickey said the crash site had been secured and the NTSB was expected to be on the scene early in the morning of Nov. 1.

The Federal Aviation Administration, in a separate statement, said it was also investigating the accident. The flight would have been performed under an experimental permit that Scaled Composites holds from the FAA’s Office of Commercial Space Transportation.

At the press conference, officials declined to speculate on the cause of the accident. Another briefing is planned for late morning or early afternoon, Pacific Time, on Nov, 1.