Cape Canaveral

The company's founder and chief executive, Elon Musk, said Monday that these struts had flown many times before without any problem. But two minutes into the June 28 launch, one of the struts in the second stage of the unmanned Falcon 9 rocket likely broke loose. The strut was holding down a helium bottle in the liquid oxygen tank.

Musk says if the strut snapped as engineers believe, the helium bottle would have shot to the top of the tank at high speed, dooming the rocket and its Dragon supply ship for the International Space Station.

The accident happened about 2 1/2 minutes into the flight from Cape Canaveral, Florida. 

A billowing white cloud emerged in the sky, growing bigger and bigger, then fiery plumes shot out of where the rocket was supposed to be, and pieces could be seen falling into the Atlantic. 

More than 5,200 pounds of space station cargo were on board, including the first docking port designed for future commercial crew capsules.