An Israeli news website is one of many sources confirming the IDF was responsible for the Qana massacre.
http://www.ynetnews.com/articles/0,7340,L-3285572,00.html2 August 2006
"The Israel Defense Forces on Wednesday evening published its formal investigation regarding the aerial strike on Qana , in which 27 Lebanese civilians were killed. IDF sources state that their work assumption was that the building was emptied of civilians and was being used as a cover for terrorists.
"Had we known the building was occupied by civilians, we would not have attacked it," they said.
On Sunday, a building in Qana was bombed by the IDF and later collapsed. According to Lebanese claims, the building was being used as a shelter for south Lebanon refugees. The area incurred vast damages and rescue operations lasted for hours.
Pursuant to this, Defense Minister Amir Peretz instructed the IDF to conduct an immediate investigation of circumstances surrounding the incident. In the mean time, the IDF announced a 48 hour cessation of aerial attacks.
Findings confirm initial statements
The investigation reveals that, prior to the attack on the building housing the civilians, several other structures were attacked in the same area, because they served as terrorist infrastructure.
Findings, which were presented to the Chief of General Staff Lt. Gen. Dan Halutz authenticated previous IDF statements regarding the attack: the building was struck at 00:25 Sunday by two bombs launched by the IAF. One of the bombs exploded and the other was apparently a dud..."