Explosion at SpaceX launch pad destroys rocket, satellite

A massive fireball and explosion erupted today at SpaceX's main launch pad, destroying a rocket as well as a satellite that Facebook was counting on to spread internet service in Africa.

There were no injuries. The pad had been cleared of workers before what was supposed to be a routine pre-launch rocket test.

SpaceX Chief Elon Musk said the accident occurred during the fuelling of the rocket and originated around the upper-stage oxygen tank.

"Cause still unknown," Musk said via Twitter.

"More soon."

The explosion - heard and felt for miles around - dealt a severe blow to SpaceX, still scrambling to catch up with satellite deliveries following a launch accident last year.

It's also a setback for NASA, which has been relying on the private company to keep the International Space Station stocked with supplies and, ultimately, astronauts.

SpaceX was preparing for the test firing of its unmanned Falcon rocket when the blast occurred shortly after 9.00 am at Cape Canaveral Air Force Station.

The test was in advance of Saturday's planned launch of an Israeli-made communications satellite that was supposed to provide home internet for parts of sub-Saharan Africa and the Middle East.

A video of the explosion shows a fireball enveloping the top of the rocket. Moments later, the payload fairing plunged to the ground, followed by more explosions.

Buildings four miles away shook from the blast, and a series of explosions continued for several minutes. Dark smoke filled the overcast sky.

A half-hour later, a black cloud hung low across the eastern horizon.

TV cameras showed smoke coming from the launch pad five hours later. Most of the rocket was still standing, although the top third or so was clearly bent over.

The explosion occurred at Launch Complex 40 at the Air Force station, right next door to Kennedy Space Centre, where emergency staff was on standby following the accident. At the same time, personnel were monitoring the air for any toxic fumes.

The Air Force stressed there was no threat to public safety in the surrounding communities.

The initial blast sent next-door NASA employees rushing frantically outside to see what happened.

Because the pad was still burning, it remained off-limits to everyone as the afternoon wore on.