A powerful New Glenn rocket owned by Jeff Bezos' Blue Origin exploded in a spectacular fireball Thursday, sending billowing clouds of fire, smoke and flaming debris into the night sky in a tremendous conflagration visible for miles around.

The explosion occurred around 9 p.m. EDT as engineers were counting down to a brief test firing of the New Glenn's seven methane-fueled BE-4 first stage engines at the Cape Canaveral Space Force Station. Blue Origin was gearing up for a June launch to put a batch of Amazon "Leo" internet satellites into orbit.

As the engines appeared to begin firing, something clearly went wrong at the base of the rocket. The 188-foot-tall first stage became enveloped in a rapidly growing fire and moments later, the 86-foot-tall upper stage could be seen tilting and starting to fall as the first stage apparently began collapsing.

Then the vehicle suddenly exploded as its load of methane fuel and liquid oxygen ignited in a roiling fireball.

The rocket was destroyed, and as the smoke cleared, there was no sign of the erector-gantry used to move the New Glenn from its hangar to the pad and to raise it from horizontal to vertical. Likewise, one of two tall lightning towers was no longer visible.

The Amazon Leo satellites were not on board for the hot-fire test.

The cause of the explosion and what might be required to fix the problem will await a detailed analysis of telemetry and launch pad video. As for the pad, video from news helicopters well after the explosion showed multiple fires and apparently severe damage.

"All personnel are accounted for and safe," Bezos said in a social media post. "It's too early to know the root cause but we're already working to find it. Very rough day, but we'll rebuild whatever needs rebuilding and get back to flying. It's worth it."

The U.S. Space Force Eastern Range, which coordinates all launches from Florida, said in a statement that "emergency responders are on the scene. All personnel have been accounted for and there were no injuries/fatalities.

"Range officials, in coordination with Blue Origin and appropriate partners, are currently evaluating available data to determine the exact cause of the anomaly.

"Additional information will be released as it becomes available. The Eastern Range remains fully mission capable and continues to support operations at all other launch complexes."

SpaceX founder Elon Musk said in a reply to Blue Origin: "Sorry to see this, I hope you recover quickly."

It was the first such on-pad explosion at the Cape since a SpaceX Falcon 9 rocket blew up on nearby pad 40 on Sept. 1, 2016. The failure later was blamed on the rupture of a high-pressure helium tank inside the rocket's upper stage liquid oxygen tank.

Falcon 9's did not return to flight for three-and-a-half months and the pad was out of action for more than a year. In the meantime, the company relied on pad 39A at the Kennedy Space Center for Florida launches and pad 4-East at Vandenberg Space Force Base in California.

Blue Origin only has one New Glenn pad, the one that was damaged in the Thursday test.

The New Glenn, which has launched three times, is a heavy lift rocket designed to compete head-to-head with SpaceX Falcon 9 and Falcon Heavy rockets. During New Glenn's most recent flight in April, an upper stage malfunction prevented a commercial internet satellite from reaching its planned orbit.

The Federal Aviation Administration, after reviewing Blue Origin's failure analysis, cleared the New Glenn to resume flights.

Its fourth flight had been planned for early June. The New Glenn destroyed Thursday was to send 48 Leo internet satellites owned by Amazon into space. The Leo system, using a variety of rockets, will compete with Musk's Starlink satellites to provide high speed space-based internet service to users anywhere in the world.

The New Glenn also plays a key role in NASA's Artemis moon program. NASA's next Artemis mission, scheduled for launch next year, will test rendezvous and docking procedures in low-Earth orbit using moon landers built by SpaceX and Blue Origin.

NASA plans to follow that flight with one and possibly two moon landing missions in 2028. Which lander will be used for which mission has not yet been determined.

Blue Origin had planned to launch a cargo version of its moon lander on a test flight before the end of the year, using New Glenn rockets for that flight and the Artemis mission in Earth orbit. How Thursday's mishap might play into those plans remains to be seen.

"NASA is aware of the anomaly that occurred tonight at Launch Complex 36 involving Blue Origin's New Glenn rocket at Cape Canaveral Space Force Station," NASA Administrator Jared Isaacman said on social media.

"Spaceflight is unforgiving, and developing new heavy-lift launch capability is extraordinarily difficult. We will work with our partners to support a thorough investigation of this anomaly, assess near-term mission impacts, and get back to launching rockets."

He promised to "provide information on any impacts to the Artemis and Moon Base programs as it becomes available."