Emergency services are racing to the scene after a SpaceX rocket exploded while on the launch pad at Cape Canaveral.
Plumes of black smoke could be seen from several miles away shortly before 9am after fire broke out during a static test.
Nasa said space exploration and technologies firm SpaceX was conducting a test firing of its unmanned rocket when the blast occurred on Thursday morning (local time).
Witnesses said the blast shook buildings for miles around and multiple explosions continued for several minutes.
The Emergency Election Sale is now live! Get 30% to 60% off our most popular products today!