From Spacex: "...Suggests that a large breach in the cryogenic helium system of the second stage liquid oxygen tank took place. All plausible causes are being

From Spacex: "...Suggests that a large breach in the cryogenic helium system of the second stage liquid oxygen tank took place. All plausible causes are being tracked in an extensive fault tree and carefully investigated." A large breach? That's... worrying. They certainly have not "figured out" why it exploded yet, they've just moved another step down the line.