CAPE CANAVERAL, Fla. (AP) — A commercial craft carrying a ton of supplies for the International Space Station ran into thruster trouble shortly after liftoff Friday, and flight controllers scrambled to fix the problem.

SpaceX founder Elon Musk said three of the four sets of thrusters on the company's unmanned Dragon capsule did not immediately kick in, delaying the release of twin solar panels for two hours.

The company said in a statement that a fuel valve was at fault, and that two sets of thrusters were needed before the Dragon could begin the maneuvers needed to get to the space station.