Thursday morning at around 9 ET, a SpaceX Falcon 9 rocket exploded while being fueled up for an engine test firing at NASA’s Kennedy Space Center in Florida. At this time, I have no info on what happened, except that the explosion occurred three minutes before the test was scheduled. The rocket was uncrewed and no one was near the pad, so no one was injured. However, it appears that the payload, an Israeli communications satellite called AMOS-6, was lost. The launch was to have been on Saturday.
My colleague Susan Matthews at Slate has more information.
Update (Sep. 1, 2016 at 19:00 UTC): Video of the explosion has been released by USLaunchReport.com:
This is bad, have no doubt. It will delay the launch schedule for SpaceX for months to come, including the first flight of the Falcon Heavy, a huge rocket that was supposed to launch late this year, and the first flight of a previously used first stage booster that relanded after being used in a launch. There have been 28 Falcon 9 launches with two failures (if you include this one, and again we don't know the cause, and it wasn't during launch).
Correction, Sept. 1, 2016: In the original headline I wrote the rocket exploded on a test stand. It was actually on the LC 40 launch pad. Parts of the pad were damaged as well.