An unmanned SpaceX rocket carrying supplies to the International Space Station broke apart Sunday shortly after liftoff. It was a severe blow to NASA, the third cargo mission to fail in eight months.

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

"The vehicle has broken up," announced NASA commentator George Diller. He said it was not clear how the disaster occurred or even when the rocket actually failed. Data stopped flowing from the rocket around 2 minutes and 19 seconds, he said. No astronauts were on board.

The California-based SpaceX was trying to figure out what happened, noting that everything appeared to go well in flight until the Falcon 9 rocket went supersonic.

More than 5,200 pounds of space station cargo were on board, including the first docking port designed for future commercial crew capsules, a new spacesuit and a water filtration system.

NASA officials said they have enough supplies for the three-person crew on board the station to last till October and still plan to send three more crewmembers up in a late July launch. NASA likes to have a six-month cushion of food and water, but is now down to four months.

SpaceX President Gwynne Shotwell assured reporters, at an early afternoon news conference, that the company will fix the problem - "and get back to flight." Shotwell said there was a pressurization issue in the upperstage.

However, she did not say what it would take to resume launches. Shotwell indicated that the company had followed all procedures with respect to safety.

Losing this shipment - which included replacements for items lost in two previous failed supply flights - was a huge setback for NASA in more than one way. The space agency is counting on private industry to transport cargo - and eventually astronauts - to the orbiting lab. The California-based SpaceX is one of the contenders.

"This is a tough day," said NASA's top spaceflight official, William Gerstenmaier. He said there was nothing common among the three accidents, "other than it's space and it's difficult to go fly."

This is the second failed station shipment in a row. In April, a Russian cargo ship spun out of control and burned up upon re-entry, along with all its precious contents. And last October, another company's supply ship was destroyed in a launch accident.

The three space station residents are in no immediate trouble because of the latest failed delivery. Late last week, NASA's space station program manager, Mike Suffredini, said the outpost had enough supplies on board to make it to October or so.

"It'll be a challenge for them, this loss will be a challenge, but it's also a learning experience. It's not whether you stumble or fall, but what you do after you stumble and fall that's going to define success, so we will pick ourselves up, we will watch the SpaceX team through this and figure this out and get back to flying, mean while we're in a good position on the ISS being able to house the crew and protect the schedule going forward and protect the research," according to NASA.

Russia expects to take another crack at launching supplies on Friday from Kazakhstan.

SpaceX, meanwhile, is one of two companies hired by NASA to start ferrying American astronauts to the space station as early as 2017. The other contender is Boeing.

SpaceX is led by billionaire Elon Musk, who also heads up Tesla, the electric car maker.

NASA will continue to investigate the root cause of the problem and is deploying vessels and resources to the debris field. If anyone finds rocket debris out on the Space Coast, you can call the NASA hotline at 321-867-2121

Information from the Associated Press was included in this report.

SpaceX Rocket Launch debris visible on radar (PHOTO/National Weather Service Melbourne).

Here is a video still sequence of the launch failure: