Three houses have been damaged and telephone lines melted during two separate arson attacks at Shantallow in Londonderry.
Some of the damage at Liscloon Drive
A fuel tank at Liscloon Drive was set on fire at around 0245 BST.
Station Commander Paul Coyle of the Fire and Rescue Service said the occupants of the house had a lucky escape.
A house and fence were also damaged when an oil tank at Drumleck Drive was set on fire shortly before midnight.
Commander Coyle said "potentially serious injuries" to residents were only avoided because fire crews prevented the blaze at Liscloon Drive from "breaking to the house".
"Perhaps what people don't realise is that when any liquid fuel ignites, it can burn extremely intensely and very rapidly and obviously this produces a great deal of heat," he said.