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NEW YORK — An unmanned rocket by Elon Musk’s SpaceX on a resupply mission to the International Space Station exploded Sunday just minutes after launch.

SpaceX said that an “anomaly” had caused the spaceship, named Dragon, to fail and was investigating. NASA is set to hold a press conference later Sunday.

“It is not clear what happened,” NASA said initially. “The vehicle has broken up.”

SpaceX — which is headed by Musk — has made seven trips to the ISS under a contract the company has with NASA. It is the first company to complete a return trip to the space station, a feat previously achieved by only governments.

The failed cargo flight was carrying more than 2 tons of supplies, including 1,500 pounds of food and provisions for the crew aboard the space station.

In a statement, NASA Administrator Charles Bolden said the failure of the resupply mission will not affect the safety of the astronauts on board. Current supplies should last for several months and resupply flights by other operators are scheduled in coming months.

Three space station astronauts, two Russians and NASA’s Scott Kelly, were awaiting the arrival of SpaceX’s shipment, which was meant to arrive on Tuesday.

In a tweet from space, Kelly, who is the brother-in-law of former Arizona Congresswoman Gabrielle Giffords, said he watched the launch. “Space is hard,” he wrote.

SpaceX’s mission is the latest failed attempt to resupply the International Space Station, a laboratory that has been orbiting earth since 1998 and operated jointly by Russia and the U.S.

Dragon was also meant to bring nearly 1,400 pounds of supplies in its return trip. The spaceship was scheduled to land in the Pacific Ocean off the coast of Baja, California, in about five weeks.

In late April, Russia had to abandon a trip to the ISS after its spacecraft carrying 3 tons of cargo lost control.

And last October, a cargo spacecraft developed by Orbital Sciences destined for the ISS exploded just after the company was awarded a $1.9 billion contract with NASA. (Orbital Sciences became known as ATK after merging with the aerospace arm of Alliant Techsystems Inc. in February.)

Separately, one life was lost last fall — just days after the Orbital Sciences incident — when a craft developed by Virgin Galactic intended for eventual civilian passengers exploded during a flight over California.

Sunday’s launch from Cape Canaveral in Florida was supposed to be the third attempt by SpaceX to recover the rocket that launches its spacecraft.

Typically, the expensive rockets that give spaceships their initial lift are discarded into the ocean after takeoff. In an attempt to recover and reuse those rockets, SpaceX developed a floating platform for the ejected rocket to land on.

SpaceX has made two previous attempts to land the first stage of its Falcon 9 rocket — once in January and again in April. Both attempts at landing failed.

The ability to recover launch rockets is expected to move space travel further toward a future in which people, satellites and other items can be inexpensively launched into orbit.

SpaceX plans to launch its first rocket with humans on board in 2017.