More than 48 hours since the explosion on the Gaza Strip beach that killed seven Palestinian civilians, the mystery surrounding the blast is still far from being resolved. The Israel Defense Forces team investigating the incident, under Major General Meir Klifi, continued its work on Sunday, but the army was still hard-pressed to offer a definitive answer on what caused the explosion. At this time there are three possible explanations:

1. An off-target IDF shell: This appeared to be the most likely scenario during the initial stages of the investigation, however, as it advances there is growing skepticism about it. The head of the Southern Command, Major General Yoav Galant, said Sunday: "There is more than a single piece of evidence that counters the possibility that this [incident] involved artillery shelling. Our shelling ended at 4:51 P.M. [on Friday]. Our observation sources scanned the beach by 4:58 P.M. and they did not witness any unusual activity. This raises serious questions." In addition to the inconsistency between the time of the shelling and the time of the explosion Palestinian witnesses believe the latter was between 5 P.M. and 5:15 P.M. there is a discrepancy between the programming of the shells' target and the actual site of the incident. Sunday, the Palestinians agreed to an Israeli request and released details of the precise location of the incident. Out of six shells fired, five had targeted an area approximately 250 meters north of the site of the actual blast. The first shell, which was not programmed to hit a specific target, was fired at 4:32 P.M., and landed in the northernmost part of the area in question i.e., furthest from the site of the incident.

2. Unexploded IDF ordnance: In the past months the IDF has fired hundreds of shells in the area of Friday's incident. In some instances, Palestinian civilians were killed when they touched the unexploded shells including youths who sought to dismantle the ordnance in order to sell the metal. Israel has no means of pinpointing the location of the unexploded ordnance from previous operations.

3. Detonation of a Palestinian bomb: Less than two weeks ago Israeli naval commandos operated in the northern Gaza Strip and ambushed a team of Qassam rocket operators. The Palestinians reported that groups of divers had arrived by sea, and militant forces announced that they would find ways to prevent any similar operations in the future. The possibility does exist that areas near the beach were mined and that the family members accidentally set off an explosive device that was intended to destroy a team of Israeli special-forces troops. Possible evidence of this hypothesis are Palestinian eye-witnesses who said that Hamas militants rushed to the site of the blast on Friday evening to collect remnants of the explosives.

Meanwhile, IDF sources reported last night that there is still no breakthrough in the investigation. Defense Minister Amir Peretz instructed the IDF on Saturday to present him with their final conclusions of the incident by Tuesday evening at the latest.

The key to solving the mystery will be in the analysis of the remnants of the shell or bomb that killed and injured the civilians. Three of those injured are hospitalized in Israel. If they were hurt by shrapnel, its origins can be determined.