The unmanned rocket was preparing to launch a communications satellite and was due to take off on Saturday
There has been an explosion at the SpaceX launch site in Florida, shaking buildings and sending smoke billowing into the sky.
Elon Musk's firm was carrying out a routine test firing of its unmanned rocket at Cape Canaveral Air Force Station when the explosion happened.
The Falcon 9 rocket and its $200m satellite payload were destroyed.
SpaceX said no-one was injured in the blast, and blamed an "anomaly" on the launch pad for the explosion.
Update on this morning's anomaly pic.twitter.com/1ogCMPCY44— SpaceX (@SpaceX) September 1, 2016
Loss of Falcon vehicle today during propellant fill operation. Originated around upper stage oxygen tank. Cause still unknown. More soon.— Elon Musk (@elonmusk) September 1, 2016
The force of the explosion shook buildings several miles away, and a thick cloud of smoke was seen rising from the launch site.
The test was being carried out in advance of a planned Saturday launch from the site, which is next to NASA's Kennedy Space Centre.
Local officials have said there is no risk to the public:
There is NO threat to general public from catastrophic abort during static test fire at SpaceX launch pad at CCAFS this morning.— Brevard EOC (@BrevardEOC) September 1, 2016
SpaceX is one of two companies shipping supplies to the International Space Station for NASA.
The company successfully launched a Falcon 9 last month, sending a Japanese communications satellite into orbit and then landing the rocket on a floating drone ship.