Hamas initially claimed that the explosion was caused by an Israeli air raid, but later acknowledged that the blast was accidental .
An Israeli military spokesman had already denied any role in the blast saying: "The armed forces have nothing to do with the Gaza explosion."
Israeli forces also arrested five members of the al-Quds Brigades and the Popular Resistance Committee in the West Bank town of Qabatiya, south of the city of Jenin, after about 30 Israeli military vehicles stormed the town at dawn on Thursday.
Since Israel and the Palestinians resumed peace talks in late November, at least 356 people have been killed in violence, according to an AFP tally.
In all, 6,319 people have been killed since the start of the second Palestinian uprising in September 2000, the vast majority of them Palestinians, according to a separate AFP count.