Landfill gas emissions can lead to environmental, hygiene and security problems in the landfill.[16][17] Several accidents have occurred, for example at Loscoe, England in 1986,[18] where migrating landfill gas accumulated and partially destroyed a property. An accident causing two deaths occurred from an explosion in a house adjacent to Skellingsted landfill in Denmark in 1991.[19] Due to the risk presented by landfill gas, there is a clear need to monitor gas produced by landfills. In addition to the risk of fire and explosion, gas migration in the subsurface can result in contact of landfill gas with groundwater.