Watch: SpaceX Rocket Headed to ISS Explodes in Midair

NASA is working to figure out why an unmanned SpaceX rocket carrying supplies to the International Space Station exploded shortly after launching from Cape Canaveral this morning, The Associated Press reports.

Among the 5,200 pounds of cargo on the rocket was a first-of-its-kind docking port for the space station that would have been used for future crew capsules.

It's a major blow for the private company SpaceX, headed by billionaire and Tesla Motors founder Elon Musk, which is supposed to begin transporting astronauts to the space station for NASA as soon as 2017. The last seven SpaceX shipments to the space station have been successful.