US officials have not determined whether President Saddam Hussein was inside the building in Baghdad's Mansour neighbourhood after it was bombed by a US Air Force B-1B Lancer.
Workers must sift through the building's rubble to locate any remains and then test them, Defence Department officials said.
The BBC reported last night that UK security sources said they believed Mr Saddam may have escaped Monday's blast.
The target was a deep bunker under a restaurant located in an exclusive area of the Iraqi captial. US intelligence had been tipped off that Mr Saddam has just gone there. All that was left yesterday was a gaping crater 60 feet deep.
B-1B is the backbone of the US long-range bomber force providing massive and rapid delivery of precision and non-precision weapons against any potential adversary anywhere around the globe on short notice.
The man who may have killed President Saddam and his two sons was told "This is the big one" when his bomber was diverted from a mission in western Iraq. The four crewmen on the Lancer did not know exactly what that meant.
But 12 minutes later they had diverted from their original plan, sped some 200 miles to Baghdad and dropped four huge bombs on a suspected hiding place of Mr Saddam, his sons and other regime leaders, said bombardier Lieut Col Fred Swan.
"When we got the word that it was a priority leadership target, immediately you get kind of an adrenaline rush," Col Swan said yesterday. "But then you fall back to your original training that says 'Hey, let's get the job done'."
That meant cross-checking the target co-ordinates three times, arming the weapons, turning the jet to fly to Baghdad and finally releasing the bombs, including two "bunker-busters".