Why might a large explosion shake the home of a senior Hamas military commander in the Gaza Strip?

The BBC even-handedly report enthusiastically first that 'Palestinians said (it) was caused by an Israeli missile strike.' and then reluctantly second that 'However, Israel's military denied any involvement, saying it had not launched any strikes in the area.'

Now why might a house belonging to a senior Hamas military commander in the Gaza Strip suddenly explode? How about a workplace accident with explosives? It's a possibility that even the BBC do report 'The cause of the explosion was not immediately clear, but militants have sometimes been killed unexpectedly while preparing bombs and not in direct conflict.' But you can tell they're not happy about it and would rather blame those nasty Israelis.