Agatha Christie never thought of this -

Glen

but the reports are suggesting that nat gas was the murder weapon. The neighbours reported smelling gas - 2 houses levelled, numerous deemed unsafe, 4 dead. It is truly sad that 2 neighbours were caught in the blast. Google explosion in Edmonton. I am sure we will get a report at the Gas Safety Council -

Steamhead

Here's the link

http://www.edmontonsun.com/news/edmonton/2010/06/21/14468796.html