SpaceX Falcon 9 rocket explodes minutes after launch

An unmanned SpaceX rocket exploded minutes after launch Sunday morning, destroying cargo meant to resupply astronauts on the International Space Station.

The Falcon 9 rocket exploded about 2 minutes 19 seconds after liftoff from the Cape Canaveral Air Force Station in Florida, NASA confirmed Sunday. The explosion occurred during the seventh mission of a $1.6 billion contract SpaceX has with NASA to provide 15 cargo flights to deliver equipment and supplies to the space station.

"We appear to have had a launch vehicle failure," NASA commentator George Diller said following the explosion.

SpaceX CEO Elon Musk said an over pressurization occurred in the liquid-oxygen tank of the rocket's upper stage.

"That's all we can say with confidence right now," Musk said via Twitter. "Will have more to say following a thorough fault tree analysis."

A SpaceX representative declined to provide additional comment.

While the rocket was carrying 4,000 pounds of equipment, supplies and science gear for astronauts in the space station, a primary goal of the mission was to make a third attempt to land the rocket's first stage on an off-shore remotely-operated barge. Attempts in January and April to land the reusable Falcon 9 rocket on a landing pad ended in explosions when rockets hit the barge too hard.

The gear lost in the explosion included the first of two new docking adapters being built by Boeing and SpaceX as part of companies' ambitions to ferry astronauts to the International Space Station. SpaceX hopes to begin taxiing astronauts to the space station as early as 2017 under a $2.6 billion contract the Hawthorne, Calif.-based company won from NASA last year.

Also destroyed in the explosion were two pairs of Microsoft's HoloLens, the augmented reality headset unveiled in January. In a partnership dubbed "Sidekick," the headsets were intended to "provide virtual aid to astronauts working off the Earth, for the Earth," NASA said in a statement Thursday.

The goal of the project is to provide astronauts with assistance as they need it. The hope is that the devices will help reduce crew training requirements while increase the efficiency at which work can be performed in space.

The loss of the cargo aboard the rocket doesn't imperil the astronauts aboard the space station, who still have about four months of supplies, NASA said.

"We are disappointed in the loss of the latest SpaceX cargo resupply mission to the International Space Station," NASA Administrator Charles Bolden said in a statement following the explosion. "However, the astronauts are safe aboard the station and have sufficient supplies for the next several months."

The Russians plan to launch another Progress craft on July 3 to resupply the station, its first since an April 28 failure.

Updated at 9:45 a.m. PT with Musk's comment on explosion.