CAPE CANAVERAL, Fla. >> An unmanned commercial supply rocket bound for the International Space Station exploded moments after liftoff Tuesday evening, with debris falling in flames over the launch site in Virginia. No injuries were reported following the first catastrophic launch in NASA’s commercial spaceflight effort.

The accident at Orbital Sciences Corp.’s launch complex at Wallops Island was sure to draw criticism over the space agency’s growing reliance on private U.S. companies in this post-shuttle effort.

NASA is paying billions of dollars to Orbital Sciences and the SpaceX company to make station deliveries, and it’s counting on SpaceX and Boeing to start flying U.S. astronauts to the orbiting lab as early as 2017.

The Orbital Sciences’ Antares rocket blew up over the launch complex. The company said everyone at the site had been accounted for, and the damage appeared to be limited to the facilities. And nothing on the lost flight was urgently needed by the six people living on the space station 260 miles into space, officials said.

Flames could be seen shooting into the sky as the sun set.

Orbital Sciences’ executive vice president Frank Culbertson said things began to go wrong 10 to 12 seconds into the flight and it was all over in 20 seconds when what was left of the rocket came crashing down. He said he believes the range-safety staff sent a destruct signal before it hit the ground, but was not certain at this point.

Bill Wrobel, director of NASA’s Wallops Flight Facility, said crews are letting the fire burn out and have set up a perimeter to contain them in the darkness.

This was the second launch attempt for the mission. Monday evening’s try was thwarted by a stray sailboat in the rocket’s danger zone. The restrictions are in case of just such an accident that occurred Tuesday.

Culbertson said the top priority will be repairing the launch pad “as quickly and safely as possible.”

“We will not fly until we understand the root cause,” he said, noting that it is too soon to know how long that will take.

The Wallops facility is small compared to major NASA centers like those in Florida, California and Texas. Those who work at Wallops Island joke that even people living on Virginia’s Eastern Shore are surprised to learn about rocket launches there.

Michelle Murphy, an innkeeper at the Garden and Sea Inn, New Church, Virginia, where launches are visible across a bay about 16 miles away, saw the explosion.

“It was scary. Everything rattled,” she said. “There were two explosions. The first one we were ready for. The second one we weren’t. It shook the inn, like an earthquake. It was extremely intense.”

Culbertson advised people not to touch any rocket debris that might wash ashore or that came down on their property because hazardous materials were aboard.

Right afterward, the roomful of engineers and technicians were ordered to maintain all computer data for the ensuing investigation. Culbertson advised his staff not to talk to news reporters and to refrain from speculating among themselves.

“Definitely do not talk outside of our family,” said Culbertson, a former astronaut who once served on the space station.

It was the fourth Cygnus bound for the orbiting lab; the first flew just over a year ago. SpaceX is scheduled to launch another Dragon supply ship from Cape Canaveral in December.

The Cygnus cargo ship Tuesday had held 5,000 pounds of experiments and equipment. By coincidence, the Russian Space Agency was proceeding with its own supply run on Wednesday, planned well before the U.S. mishap.

Among the instruments that were lost: a meteor tracker and 32 mini research satellites, along with numerous experiments compiled by schoolchildren.

The two Americans, three Russians and one German on the orbiting space station were watching a live video feed from Mission Control and saw the whole thing unfold before their eyes, said NASA’s space station program manager Mike Suffredini. They were keeping abreast of what was happening,

Until Tuesday, all of the supply missions by the Virginia-based Orbital Sciences and California-based SpaceX had been near-flawless.

President Barack Obama has long championed this commercial space effort. He was in Wisconsin for a campaign rally and was kept abreast of the accident.

SpaceX’s billionaire founder and chief officer Elon Musk — whose company is the face, in many ways, of the commercial effort — said he was sorry to learn about the failure. “Hope they recover soon,” he said in a tweet.

Support poured in from elsewhere in the space community late Tuesday night.

“Very sorry to see the Antares rocket launch failure,” said Chris Hadfield, a former Canadian astronaut who served as space station commander last year. “Spaceflight is hard. Very glad that no one was hurt.”

John Logdson, former space policy director at George Washington University, said it was unlikely to be a major setback to NASA’s commercial space plans. But he noted it could derail Orbital Sciences for a while given the company has just one launch pad and the accident occurred right above it.

The explosion hit Orbital Science’s stock, which fell more than 15 percent in after-hours trading.

___

AP Science Writer Seth Borenstein reporting from Washington and Associated Press writer Alex Sanz in Atlanta contributed to this report.