U.S. defense officials indicate the remote southern Afghan area where American aircraft are alleged to have killed or wounded scores of civilians is an active area of hostile Taleban activity.
U.S. defense officials said American, Afghan, and other coalition forces had several gunbattles in the area north of Kandahar in recent weeks.
They also report several detainees were taken in connection with the fighting Monday that allegedly led to the civilian Afghan casualties.
Lieutenant General Gregory Newbold of the Pentagon's Joint Staff said soldiers also found a cache of about 15 tons of ammunition, including anti-aircraft munitions.
"A coalition reconnaissance element found a cache near this site, Deh Rawud, very recently, in the past couple of days, that including 15 tons of munitions, including anti-aircraft weapons and that is a lot of ammunition, but it is symptomatic of the area and the capabilities that they have," Mr. Newbold said.
The Pentagon said a U.S. Air Force AC-130 gunship equipped with a cannon and heavy machine guns fired on six sites in the area late Sunday and early Monday. Officials concede this firing could have been responsible for civilian casualties.
But they also said the AC-130 had come under anti-aircraft fire and said other coalition aircraft had been fired on in the same area in recent weeks.
The incident occurred at about the same time a U.S. B-52 bomber dropped munitions on a cave and bunker complex nearby, a move reminiscent of earlier phases of the war on terrorism.
General Newbold said that target was hit because fighting emplacements had been observed outside the entrances to the caves and bunkers. He says they were not occupied, but represented a strongpoint that Taleban fighters could man and threaten coalition forces.
A joint U.S.-Afghan team is in the area north of Kandahar investigating the incident. Local reports say 40 people may have been killed by the U.S. air attack and 100 others wounded. But U.S. officials have only confirmed 21 wounded civilians.
A report from the scene quotes a military spokesman as saying American forces detected an anti-aircraft gun firing repeatedly on U.S. aircraft from a compound where 25 people attending a wedding party were reportedly killed.
But the spokesman for the fact-finding mission is also quoted as saying no wreckage of the gun has been found.