U.S. officials said they would take reporters and Afghan government representatives to the site of a U.S. bombing in Uruzgan province in central Afghanistan that reportedly killed civilians.

Residents and officials said dozens of civilians, including women and children, were killed in the attack there early Monday. Afghan estimates of those killed ranged from about 40 to more than 100. The military was offering the tours Tuesday.

U.S. military officials said any of three things could have caused the civilian casualties: An errant bomb from a U.S. B-52, a raid by a U.S. AC-130 plane on anti-aircraft sites or anti-aircraft fire falling back to the ground.

Lt. Cmdr. Jeff Davis, a Pentagon spokesman, said Monday that the B-52 dropped seven precision-guided, 2,000-pound bombs on cave and bunker complexes in the same general area of Uruzgan province. One went astray.

During that operation -- which involved an undisclosed number of regular and special U.S. forces -- an American forward air controller on the ground reported fire from anti-aircraft artillery sites and called in the AC-130 gunship to counterattack, Davis said.

Afghans brought four injured children, ranging in age from 8 months to 5 years, to U.S. forces in the area, Davis said. The Americans took the injured children, accompanied by an Afghan adult, to a U.S. military hospital in Kandahar, Davis said.

It was not clear Monday how close the anti-aircraft sites were to the caves and bunkers being bombed.

Whatever the explanation, the matter is a reminder that the mission in Afghanistan is dangerous, not only for American and allied forces searching for Al Qaeda and Taliban fighters but also for Afghan civilians. If the attack turns out to have been a deadly error by U.S. forces, it would not be the first time that human or mechanical error led to unintended deaths and injuries there.

Just last week, U.S. Central Command said it had determined that two U.S. Air National Guard F-16 pilots were primarily to blame for the mistaken bombing in April of Canadian forces in southern Afghanistan. One pilot dropped a 500-pound bomb that killed four Canadian soldiers and injured others.

On May 31, U.S. troops mistakenly killed three of their Afghan allies in a firefight that broke out when both sides moved separately into a compound mistakenly thought to be a hide-out of Taliban and Al Qaeda leaders.

About 7,000 U.S. troops are in Afghanistan. They have conducted little aerial bombing in recent months and have engaged in little direct ground combat since March.