(Story was updated to include additional information and quotes from the NASA press conference, which concluded around 10 p.m. local time.)
An unmanned Orbital Sciences Corp. rocket exploded seconds after liftoff Tuesday from a launch pad in Virginia.
The company's $200 million Antares rocket topped with a Cygnus spacecraft suffered a "catastrophic anomaly" at 6:22 p.m. local time in what would have been its third mission to resupply the International Space Station.
"Teams were not tracking any issues prior to launch," one official said on NASA TV, which was live-streaming the event.
There were no injuries reported and all personnel were accounted for after the explosion at the space agency's Wallops Flight Facility on Virginia's Eastern Shore, about 160 miles southeast of Washington, D.C. Photographs show the explosion was visible from nearby residences.
Orbital has formed an anomaly investigation board that will work with NASA and the Federal Aviation Administration to determine the cause of the mishap, the company said in a statement.
"It is far too early to know the details of what happened," Frank Culbertson, executive vice president and general manager of the firm's Advanced Programs Group, said in the release.
He was among several officials who participated in a press conference later in the evening and advised residents in the region not to touch or collect any suspected debris, which may be contaminated with toxic fuel and other harmful material.
"Certainly don't go souvenir-hunting on the beach," he said.
Orbital and Space Exploration Technologies Corp., known as SpaceX and headed by billionaire Elon Musk, have NASA contracts to ferry cargo to the space station.
After retiring its shuttle fleet in 2011, the space agency turned to the private sector to resupply the station with water, food and other supplies. It depends on Russia to ferry astronauts to and from the orbital outpost, though recently awarded SpaceX and Boeing deals to develop spacecraft to do the job.
During the press conference, officials said there is enough sustenance aboard the station to sustain astronauts through March -- months after SpaceX's next planned resupply flight in early December. They couldn't say how the failure might affect congressional support for the so-called commercial crew program to fund privately developed human-rated spacecraft.
Orbital and SpaceX want to challenge United Launch Alliance LLC, a Boeing Co.-Lockheed Martin Corp. joint venture, in competing to launch medium-sized military and spy satellites as part of the Air Force's Evolved Expendable Launch Vehicle, or EELV, program.
Antares is Orbital's newest and biggest rocket, and it employs Soviet-era engines. The two-stage booster, initially developed for the defense market, for its first stage uses two liquid-fuel AJ26 engines, made by Aerojet, part of California-based GenCorp Inc. They’re modified versions of the NK-33s built in Russia more than four decades ago for its moon program, which was later canceled.
Aerojet bought about 40 NK-33 engines in the mid-1990s and, under a contract with Orbital, modified them specifically for Antares, according to Aerojet. The second-stage of the rocket uses a solid-fuel engine made by Arlington, Virginia-based Alliant Techsystems Inc.
When asked why the company selected the Russian engines, Culbertson said officials still don't know whether the propulsion system caused Tuesday's failure. He acknowledged the engine was "designed to carry cosmonauts to the moon," and described it as a "very robust and rugged" design that was tested extensively before launch without any suspected problems.
"There are not many other options around the world of using power plants of this size and certainly not in this country, unfortunately," he said.
Culbertson estimated the cost of the Antares rocket and Cygnus spacecraft at about $200 million. He said a portion of the cost of the launch was insured, but didn't specify any details. Neither he, nor other officials, said how much it might cost to fix the launch pad, which news outlets reported was significantly damaged.
Orbital and ATK's defense units earlier this year announced a plan to merge in a $5 billion deal to create Orbital-ATK. Shareholders are expected to vote on the merger Dec. 9.
Here's video of the launch and explosion: