GAZA STRIP - An explosion ripped through a bomb-maker's house in the northern Gaza Strip Thursday, killing seven people and wounding up to 40 others.

According to Palestinian sources, five of the injured are in serious condition.

The two-story house, which was completely destroyed, belonged to one of the terror group's senior commanders and expert bomb makers, Ahmed Hamouda.

The huge explosion damaged other buildings, both residences and businesses, in the neighborhood.

At first, Hamas blamed the incident on an Israeli air strike, but on Friday a spokesman admitted the explosion had been an accident.

There have been many such "work" accidents in Palestinian explosives manufacturing facilities and warehouses, often located in densely populated areas.

Two months ago, a similar incident killed three Hamas operatives. It is standard procedure to blame Israel.

Sources: YNet news, Haaretz, The Jerusalem Post