U.S. officials say a massive air strike in Pakistan Friday targeted al Qaeda's second in command using unmanned Predator aircraft and military jets based in Afghanistan.
The strike was based on CIA information that Ayman al-Zawahiri, Osama bin Laden's top lieutenant, was at the location or about to arrive.
This morning, CIA officials remained optimistic about the strike, but there still has been no confirmation that Zawahiri was among those killed at the scene.
However, Pakistani officials now have told the Associated Press they have information that Zawahiri was not at the scene, though it's not clear how they know that.
U.S. officials tell ABC News the bodies were badly burned in the attack, and they have obtained tissues samples that will be flown to Washington for a possible DNA match.
Pakistan-Afghan Border Strike
The attack took place early Friday morning Pakistan time in a small village a few miles from the border with Afghanistan.
Villagers described seeing an unmanned plane circling the area for the last few days and then bombs falling in the early morning darkness.
Eighteen people were killed, according to the villagers, who said women and children were among the dead.
Pakistani officials tell ABC News that five of those killed were high-level al Qaeda figures and their bodies are now undergoing forensic tests for positive identification.
"We are definitely investigating whether a high-profile terrorist was killed there or not," said Sheikh Rashid Ahmed, Pakistan's information minister.
Officials say Ayman al-Zawahiri was known to have used safe houses in the area last winter and was believed to be in the area again this winter.
Zawahiri, who appeared last week in a new video, increasingly has seemed to be taking the operational reins of al Qaeda, and is thought by U.S. officials to be the current true mastermind of the terrorist group.
This story is based upon a report by ABC News' Brian Ross for "Good Morning America Weekend Edition."