"He said the explosion heard by locals was likely to be a sonic boom - a series of shockwaves caused by the enormous speed of the meteor.

"The noise doesn't indicate it hit anything - it probably burnt up in the atmosphere," Dr Drinkwater said. "

It wouldn't be a sonic boom. It hit the atmosphere at high speed and exploded. You could call a car crashing into a wall, a high speed deceleration, similarly this was an extremely high speed deceleration- a rock ploughing through air so fast the air can not get out of the way, compressing and heating up creating the tail of hot gases. Air pressure in front of rock increasing to the point of exerting enough gees that the rock breaks apart thereby suddenly increasing it's total drag thereby increasing the heat even further, breaking rock more, more heat, more rock breaking up, all it this occuring in miliseconds- Boom! And this explosive power could in the range of nuclear bombs- usually exploding several miles up and therefore not doing any serious damage to those on the ground.
Hmm, I wonder if people living at high altitude- say, the mile high city of Denver are at a significantly higher risk from the explosions from such fireballs?