NASA: A mishap occurred

NASA: "A mishap occurred shortly after liftoff. Orbital has declared a contingency. NASA and Orbital are still determining when a press conference will be held."

UPDATE: 646 pm EST: The Orbital Sciences Corp.'s Antares rocket lifted off to start its third resupply mission to the International Space Station, but suffered a catastrophic anomaly shortly after liftoff at 6:22 p.m. EDT. No injuries have been reported, and Orbital reports that all personnel around the Wallops Flight Facility launch site have been accounted for. NASA will continue to provide additional updates as they become available, as well as the earliest expected time for a news conference.