"The IDF is innocent," was the bottom line that came out of a press conference Tuesday night, during which Defense Minister Amir Peretz, Chief of General Staff Lt.-Gen. Dan Halutz and other top officers presented the findings of an internal military investigation into Friday's explosion that killed seven Palestinians as they picnicked on a Gaza beach. In a press conference at the Defense Ministry in Tel Aviv, Peretz told reporters that following an extensive three-day investigation the IDF had collected sufficient evidence to prove that Friday's explosion was not caused by Israel. The evidence was being presented first and foremost to the Israeli people, Peretz emphasized, saying, "We owe it to ourselves to know that we did not cause these deaths." "We have sufficient evidence which confirms our suspicion that the attempts to portray this incident as caused by Israel were wrong," Peretz said. "I know it is difficult to explain this, but the facts that have accumulated prove that Israel was not behind the incident." In contrast to daily Palestinian rocket attacks against Israel, Peretz added, the IDF made great efforts to avoid harming innocent Palestinians. "In all IDF operations one of the issues that is taken into consideration and sometimes adds risk to ourselves is the need to not cause harm to innocent civilians," the defense minister said. Halutz said that, while the IDF expressed regret immediately following the incident, it did not mean to take upon itself responsibility for the explosion. Referring to Tuesday's missile strike on an Islamic Jihad terror cell in Gaza that killed eight innocent Palestinians, Halutz stressed that the rocket cells operated from within densely populated areas. "We will not let them get away with their attacks and the [responsibility] for the price the Palestinians are paying lies on the shoulders of the Palestinian Authority and the other groups that should be doing everything possible to prevent these events from occurring," Halutz said. Peretz also expressed regret for the harm caused to innocent civilians in Tuesday's missile strike. But, he said, "all the organizations attacking us are trying to hurt our civilians. They act from within population centers while knowing that they are endangering the population." "The bottom line," Halutz said, "is that we are very sad that innocent people were killed due to an explosion that happened on the seashore of the Gaza Strip but it has no connection to Israeli military activity that happened that same day." Presenting the technical findings was Deputy Head of the IDF Ground Forces Command Maj.-Gen. Meir Klifi, who headed up the investigation into the incident on Friday. Standing in front of an array of maps and movie screens, Klifi showed aerial photographs of IDF attacks on northern Gaza that day while presenting the time line of events that led to the deadly explosion on the beach. An analysis of the location of the incident together with its timing - between 16:57 and 17:10 - Klifi said, proved that Israel could not have been behind the explosion since neither the Air Force, the Navy nor artillery cannons were in action at the time. One IAF strike on the Gaza Strip that day, he said, occurred 2.5 kilometers from the scene of the explosion and two other strikes took place hours earlier. Ruling out Navy fire, Klifi said that "every 76-mm. shell fired from the navy boats can be accounted for since they all hit their targets successfully." In fact, Klifi said, "the ones that fell closest to the location of the incident were fired four hours earlier." Artillery shelling, he added, could also not have been responsible for the explosion. A piece of shrapnel taken from one of the wounded being treated in an Israeli hospital and cross-checked with 155-mm. Shells used by the IDF proved that the explosion was not caused by Israeli artillery fire. "The fragment taken out of the wounded showed absolutely that it is not connected to any [type of] Israeli ammunition used that day," Halutz said. The army, Klifi said, has also accounted for five of the six shells that were fired in the area Friday evening before the beach explosion. None of them exploded nearby, he said, adding that the one shell that was not accounted for was fired before the five others and more than 10 minutes before the blast. Peretz and Halutz did show signs of disagreement after they were both asked separately if they would be willing to allow an international third party to inspect the shrapnel sample taken from one of the wounded. Peretz said he would consider the possibility but later, after he had already left the briefing, Halutz was asked the same question by the foreign press and said he was confident with the IDF's internal probe and that there was no reason to cast doubt in its professionalism. In Gaza, Human Rights Watch military expert Marc Garlasco inspected the shrapnel at the scene and saw the wounded. He concluded that the blast was caused by an Israeli shell. However, he held open the slim possibility that it was planted there by Palestinian militants, though fragment patterns did not back that. "Our information certainly supports, I believe, an Israeli shell did come in and kill these people," he said, ruling out a land mine. Garlasco was the first independent expert to inspect the scene. Palestinians also rejected the possibility that their own explosives caused the fatal blast. "This is a false allegation, and the Israeli occupation state is trying to escape from shouldering its responsibility by accusing Palestinians without evidence or any proof," said Ghazi Hamad, a spokesman for the Hamas-led Palestinian government. "The eyewitnesses and the evidence that we have confirm that the massacre is the result of Israeli shelling, and the allegation about land mines planted by Palestinians is baseless," he said. AP contributed to this report.