We seem to have it narrowed down to:
Explosion in building or explosion in compound. (or both)
The slow information flow suggests what?
I am watching CNN International. They have identified what appears to be a hole above the large embassy seal on the front of the building. It sounds like an RPG attack.
Update from Athens: No Injuries in Terror Attack
07:38 Jan 12, '07
(IsraelNN.com) Police cordoned off streets around the American embassy Friday morning after an apparent terrorist attack that caused damage but no injuries, police reported.
The explosion occurred following the firing of a rocket-propelled grenade on the building, according to Voice of Israel government radio.
The US embassy is among the best-guarded buildings in the Greek capital.
AN RPG attack might be the only way to generate an explosion...