Fire chief Eli Barza said the initial assessment was that a gas leak caused the blast at Yabetz village in central Israel, near the West Bank.
But confusion over the identity of the dead man had raised the possibility he was a Palestinian human bomber.
"It is possible that it was a terrorist attack, but it could also be an accident, and we will have to wait for police lab results," police spokesman Gil Kleiman told French news agency AFP.
One of the victims was a 65-year-old woman whose body was found in the rubble of the house.
Three children were also slightly hurt by the blast.
The last bombing in Israel was before a 29 June ceasefire declared by Palestinian groups. Islamic Jihad claimed responsibility for that attack which blew up a grocery store-restaurant on 19 June near the city of Beit Shean in the northern Jordan valley, killing the shopkeeper and the bomber.