The Palestinian interior ministry says Monday's blast in Gaza City was caused by militants accidentally detonating explosives.
The blast destroyed a number of houses in Gaza City
A huge explosion rocked the centre of Gaza City on Monday, killing five people and injuring 20 others.
At least three houses were destroyed in the explosion, one of which Palestinian officials said was used by the militant group, Hamas, for making bombs.
Hamas has maintained that the house was the target of an Israeli air strike.
But the Israeli authorities have denied having anything to do with the incident.
The blast occurred in the eastern Shajaiyeh area of Gaza city, near the border with Israel.
"According to our investigation and eyewitness accounts, what happened in Shajaiyeh was an internal explosion resulting from a fire in a house due to an error during the making of explosives," Palestinian interior ministry spokesman Tawfiq Abu Khoussa said.
The Israeli air force has often targeted Hamas members in Gaza and the West Bank, but military sources denied they were behind Monday's blast.
Sometimes blasts are caused by the accidental detonation of weapons caches kept by militant groups, says BBC Gaza correspondent Alan Johnston.
Israel completed the evacuation of all its Jewish settlements from the territory last month.
The Israeli military is scheduled to complete the pullout of its troops from Gaza by the end of September.
Hamas is committed to continuing its armed struggle against Israel, but is currently observing an unofficial ceasefire.