Israel's Channel Two on Tuesday quoted sources in an Israeli hospital which treated survivors of the June 9 explosion as saying that some of the shrapnel removed by surgeons was from a 155mm artillery shell, which are used by Israel but not by Palestinian fighters.
Israel has fired hundreds of shells into the north of the Gaza Strip in a bid to stop Palestinian rocket attacks across the border.
The Israeli army has denied responsibility for the beach blast. At a press conference on June 13 a senior Israeli army officer said Israel had not been firing at Gaza at the time of the incident. He also said shrapnel retrieved from the beach was not from an Israeli shell.
But an army spokesman said on Tuesday that they had not denied that the explosion could have been caused by a "dud shell" set off by accident. Channel Two said a faulty shell could have been on the beach for weeks.
Israeli officials have suggested that the seven Palestinians could have been killed by a landmine planted by Palestinian forces in case of Israeli commando raids. The Hamas-led government called off a 16-month-old truce after the explosion.