Pollution worries delayed attempts to douse a huge, accidental fire at the U.K.’s Buncefield fuel depot near Hemel Hempstead, some 60 kilometers northwest of London. Firefighters and officials from the Environment Agency were concerned that foaming chemicals used to quell oil flames would escape into aquifers and rivers. Hertfordshire Fire and Rescue Service began pumping a foaming agent at a 32,000 liters per minute some 26 hours after oil tanks exploded Dec. 11, causing 36 casualties but no deaths. Half the flames were extinguished within four hours.