Fireworks Explosion

Investigators still aren't sure what happened to cause an explosion in the crowd during a fireworks display northwest of Philadelphia that injured a dozen people.

None of the injuries appears to be life-threatening, although two of the injured were flown from the scene.

Upper Merion police say the blast happened about 75 yards away from the fireworks display itself.

But investigators aren't sure whether the blast came from the actual display or whether it was from something someone had in the crowd.