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Associated Press

CAPE CANAVERAL, Fla. — SpaceX says it is still trying to figuring out what caused its rocket to break apart during liftoff nine days ago, but it's getting close.

The unmanned Falcon 9 rocket had just lifted off from Cape Canaveral, Florida, on June 28, carrying cargo for the International Space Station, when the accident occurred.

Speaking Tuesday at a conference in Boston, SpaceX founder and chief executive Elon Musk said the trouble appeared to be in the upper stage, with an overpressurization of the liquid oxygen tank. Nevertheless, the company is putting together what he calls a "super-detailed" timeline, millisecond by millisecond.

So far, he says nothing seems to fit "all the dots." But he hopes to have something definitive to say by week's end.

Musk says the accident was "a huge blow."