What caused major US rocket failure?

The builders of an unmanned supply rocket, which exploded on the way to the International Space Station, are searching for the cause of the catastrophic explosion.

Antares, built by Orbital Sciences Corp, combusted seconds after leaving a launch pad in the US state of Virginia on Tuesday.

"There are many things that can cause a failure such as this," Frank Culbertson, executive vice-president of Orbital Sciences, told the BBC.

"We have to go through every single one of them to make sure we don't miss something."