The armed wing of Hamas has admitted that a massive explosion in the Gaza Strip on Thursday was caused by militants preparing an armed operation. Seven people, including a four-month-old baby were killed in the blast, in Beit Lahiya, in the north of the strip. Hamas had initially blamed the explosion on an Israeli air strike and responded with rocket fire, but Israel denied any involvement. http://news.bbc.co.uk/2/hi/middle_east/7452540.stm

See also: A work accident
http://edition.cnn.com/2008/WORLD/meast/06/12/gaza.blast/index.html?eref=edition